THE MENACING FUNGI by George A. Wistreich Ph.D., F(AAM) RC Educational Consulting Services, Inc. 16781 Van Buren Blvd, Suite B, Riverside, CA 92504-5798 (800) 441-LUNG / (877) 367-NURS www.RCECS.com THE MENACING FUNGI BEHAVIORAL OBJECTIVES UPON COMPLETION OF THE READING MATERIAL, THE PRACTITIONER WILL BE ABLE TO: 1. Briefly describe the general features of fungi. 2. Briefly describe a common method of classifying fungal diseases (mycoses) based on the site of infection. 3. Distinguish among the various epidemiological patterns exhibited by infectious diseases. 4. Describe the features of fungi with a special emphasis on dimorphic fungi. 5. Discuss the distinguishing microscopic and related cultural properties of selected pathogenic fungi, with a special emphasis on respiratory pathogens. 6. List and briefly describe the actions of examples of anti-fungal agents used in treatment of fungal infections and/or diseases. 7. Distinguish between primary and opportunistic fungal pathogens and describe their respective habitats. 8. Recognize the distinguishing microscopic and related cultural properties of primary and opportunistic fungal pathogens. 9. Discuss the means of transmission of primary and opportunistic fungal pathogens. 10. Recognize the importance of biofilms in certain fungal infections. 11. Briefly describe the clinical forms and associated features of disease states caused by primary and opportunistic fungal pathogens. 12. List and briefly describe representative mycotoxins (fungal metabolic products) and their effects. 13. Outline the general laboratory approach followed in the diagnosis of primary and opportunistic fungal pathogens. 14. Briefly discuss the medications and approaches used in the treatment of fungal pathogens. 15. Describe the prevention and control measures used with primary and opportunistic fungal pathogens. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 2 THE MENACING FUNGI 16. Briefly discuss the current understanding of the relationship between mycotoxins and sick-building syndrome. COPYRIGHT © 2006 By RC Educational Consulting Services, Inc. TX 6-147-048 Authored by: George A. Wistreich, Ph.D., F(AAM) 2006 ALL RIGHTS RESERVED This course is for reference and education only. Every effort is made to ensure that the clinical principles, procedures and practices are based on current knowledge and state of the art information from acknowledged authorities, texts, and journals. This information is not intended as a substitution for a diagnosis or treatment given in consultation with a qualified health care professional. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 3 THE MENACING FUNGI TABLE OF CONTENTS PREFACE ..........................................................................................................................10 INTRODUCTION .............................................................................................................10 ENDEMIC, EPIDEMIC, PANDEMIC AND SPORADIC PATTERNS OF INFECTIOUS DISEASES ..........................................................................................10 GENERAL PROPERTIES OF FUNGI .............................................................................11 STRUCTURAL FEATURES .......................................................................................11 REPRODUCTION........................................................................................................13 A BRIEF WORD ABOUT CLASIFICTION ...............................................................15 CLASSIFYING FUNGAL DISEASES BASED ON THE SITE OF INFECTION.............................................................................................16 ANTI-FUNGAL AGENTS USED IN TREATMENT......................................................19 VACCINES ........................................................................................................................21 THE PRIMARY FUNGAL PATHOGENS.......................................................................21 BLASTOMYCOSIS .....................................................................................................21 GEOGRAPHIC DISTRIBUTION...........................................................................21 HABITAT ................................................................................................................21 CULTURE AND MICROSCOPIC FEATURES ....................................................21 TRANSMISSION ....................................................................................................23 CLINICAL STATES ...............................................................................................23 LABORATORY AND RELATED ASPECTS OF DIAGNOSIS...........................24 TREATMENT .........................................................................................................24 PREVENTION AND CONTROL...........................................................................24 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 4 THE MENACING FUNGI COCCIDIOIDOMYCOSIS ..........................................................................................24 HABITAT ................................................................................................................25 CULTURE AND MICROSCOPIC PROPERTIES .................................................25 TRANSMISSION ....................................................................................................26 LIFE CYCLE ...........................................................................................................27 PATHOGENESIS ....................................................................................................28 INDIVIDUALS AT RISK .......................................................................................29 CLINICAL STATES ...............................................................................................29 THE HIV-INFECTED PATIENTS .........................................................................32 SIGNS AND SYMPTOMS ................................................................................32 SOLID-ORGAN TRANSPLANT RECIPIENTS ....................................................32 LABORATORY AND RELATED ASPECTS OF DIAGNOSIS...........................33 SKIN TESTS ......................................................................................................33 TREATMENT .........................................................................................................34 PREVENTION AND CONTROL...........................................................................35 HISTOPLASMOSIS..........................................................................................................35 THE CAUSATIVE AGENTS ......................................................................................35 HABITAT .....................................................................................................................36 CULTURE AND MICROSCOPIC FEATURES .........................................................36 LIFE CYCLE ................................................................................................................37 TRANSMISSION .........................................................................................................37 EXPOSURE RISKS......................................................................................................38 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 5 THE MENACING FUNGI PATHOGENESIS .........................................................................................................38 CLINICAL STATES ....................................................................................................38 LABORATORY AND RELATED ASPECTS OF DIAGNOSIS................................40 SKIN TESTS ...........................................................................................................40 TREATMENT ..............................................................................................................41 PREVENTION AND CONTROL................................................................................41 THE IMMUNOSUPPRESSED PATIENT........................................................................42 INDIVIDUALS AT RISK ............................................................................................42 PARACOCCIDIOIDOMYCOSIS.....................................................................................42 HABITAT .....................................................................................................................42 CULTURE AND MICROSCOPIC FEATURES .........................................................42 TRANSMISSION AND PATHOGENSIS ...................................................................43 CLINICAL STATES ....................................................................................................43 LABORATORY AND RELATED ASPECTS OF DIAGNOSIS................................44 TREATMENT ..............................................................................................................44 PREVENTION AND CONTROL................................................................................45 THE OPPORTUNISTIC FUNGAL PATHOGENS..........................................................45 THE ASPERGILLOSES ...................................................................................................45 GENERAL PROPERTIES OF THE ASPERGILLI.....................................................45 HABITAT ................................................................................................................46 MICROSCOPIC AND CULTURAL PROPERTIES ..............................................46 NONPATHOGENIC AND PATHOGENIC ASPERGILLI ...................................47 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 6 THE MENACING FUNGI MYCOTOXINS .......................................................................................................47 DISEASE STATES .................................................................................................47 NOSOCOMIAL INFECTIONS.........................................................................................48 ASPERGILLUS FUMIGATUS, AN IMPORTANT PATHOGEN ....................................48 CULTURE FEATURES ...............................................................................................49 PATHOGENICITY ......................................................................................................49 SELECTED A. FUMIGATUS-ASSOCIATED DISEASES ..............................................50 INVASIVE ASPERGILLOSIS ....................................................................................50 PREDISPOSING FACTORS ..................................................................................51 GASTROINTESTINAL INVOLVEMENT ............................................................51 LIVER TRANSPLANT RECIPIENTS ...................................................................51 SIGNS AND SYMPTOMS .....................................................................................52 DIAGNOSIS ............................................................................................................52 OTHER ASPERGILLOSES CAUSED BY A. FUMIGATUS .....................................52 MAJOR SYNDROMES FOUND WITH AIDS PATIENTS .......................................54 GENERAL ASPECTS OF LABORATORY DIAGNOSIS..............................................54 TREATMENT ..............................................................................................................55 PREVENTION AND CONTROL................................................................................56 CANDIDIASIS AND CANDIDA SPECIES .....................................................................56 PATHOGENIC CANDIDA SPECIES ..........................................................................56 HABITAT ................................................................................................................57 TRANSMISSION ....................................................................................................57 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 7 THE MENACING FUNGI RISK FACTORS ................................................................................................57 MEDICAL DEVICES AND BIOFILMS ...........................................................58 CULTURE AND MICROSCOPIC PROPERTIES .................................................58 DISEASE STATES .................................................................................................60 INDIVIDUALS AT RISK .......................................................................................63 TREATMENT .........................................................................................................64 DIAGNOSIS ............................................................................................................64 PREVENTION AND CONTROL...........................................................................65 CRYPTOCOCCOSIS ...................................................................................................65 HABITAT ................................................................................................................65 MICROSCOPIC AND CULTURE PROPERTIES .................................................66 TRANSMISSION ....................................................................................................67 PATHOGENESIS ....................................................................................................67 RISK FACTORS .....................................................................................................68 CLINICAL STATES ...............................................................................................68 TREATMENT .........................................................................................................70 DIAGNOSIS ............................................................................................................70 PREVENTION AND CONTROL...........................................................................70 PENICILLIOSIS ...........................................................................................................70 GEOGRAPHIC DISTRIBUTION AND HABITAT...............................................70 CULTURE AND MICROSCOPIC FEATURES ....................................................71 TRANSMISSION ....................................................................................................71 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 8 THE MENACING FUNGI CLINICAL STATES ...............................................................................................71 SIGNS AND SYMPTOMS ................................................................................71 TREATMENT .........................................................................................................71 LABORATORY AND RELATED ASPECTS OF DIAGNOSIS...........................71 PREVENTION AND CONTROL...........................................................................72 THE MYCOTOXICOSES ............................................................................................72 THE MAJOR MYCOTOXINS................................................................................72 THE AFLATOXINS AND ERGOT POISONING.................................................73 THE SICK-BUILDING SYNDROME....................................................................74 CAUSATIVE AGENTS .....................................................................................74 SOURCES ...........................................................................................................74 SIGNS AND SYMPTOMS ................................................................................75 CONCLUDING STATEMENTS ......................................................................................75 GLOSSARY ......................................................................................................................76 TERMS .........................................................................................................................76 SUGGESTED READING AND REFERENCES .............................................................78 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 9 THE MENACING FUNGI PREFACE A number of fungus diseases (mycoses) have a restricted geographic distribution, being mainly confined to areas where the causative fungi are found in nature. However, increased domestic and international travel has led to a rise in the number of reported outbreaks and sporadic cases of such endemic diseases among individuals who normally live in places far from the areas where these diseases are present. This course presents the features of mycotic diseases that pose risks of infection for travelers, individuals who are immunocompetent, and persons who are immunocompromised as well. This course also briefly considers the potential health effects posed by moldy indoor environments. Health care personnel need to be aware and familiar with these diseases and associated conditions from the standpoint of being able to minimize the risk of infection, contribute to the accurate diagnosis, and to provide the appropriate treatment for victims. INTRODUCTION T he growth of fungi on or in humans and/or lower animals produces diseases collectively called mycoses, while respiratory, dietary, dermal, and other exposures to toxic fungal metabolic products produce the diseases collectively known as mycotoxicoses. Mycoses are frequently acquired via the inhalation of the reproductive units of fungi (spores) from an environmental reservoir (source), or by unusual growth of a fungus that is normally resident on human skin or in the gastrointestinal tract. The majority of mycotoxicoses, on the other hand, are acquired from eating contaminated foods. Fungal diseases also represent an especially important complication for immunosuppressed persons and are associated with high morbidity and mortality. Limited familiarity with many of the fungal pathogens, as well as the limited diagnostic tools available can and in several situations delay the diagnosis and treatment of mycoses. This course presents several representative fungal diseases, the general properties of the causative pathogens, together with approaches used in treatment, and prevention and control. ENDEMIC, EPIDEMIC, PANDEMIC, AND SPORADIC PATTERNS OF INFECTIOUS DISEASES D iseases are often classified in terms of how they behave within a host and within a given population. The incidence of a disease, for example, refers to the number of individuals within a population who develop a specific disease during a particular time period. A particular standard used in the classification of diseases is the frequency of occurrence. Thus, if a particular disease occurs only occasionally, it would be referred to as being sporadic, while a disease that is constantly present in a population would be considered as being endemic. In the event a large number of individuals in a given geographic area acquire a specific disease such as the viral disease influenza, in a relatively short time period, the frequency of occurrence is considered to be epidemic. In situations where a series of epidemics of a disease take place on a worldwide scale, the frequency of occurrence is called a pandemic. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 10 THE MENACING FUNGI Abbreviations Used AIDS: BAL: BMT: CDC: CT: DH: DNA: ELISA: GVH: HIV: HVAC: IA: LSD: PCM: SBS: SOTR: acquired immune deficiency syndrome bronchoalveolar lavage bone marrow transplant Centers for disease Control and Prevention computerized tomography disseminated histoplasmosis deoxyribonucleic acid enzyme-linked immunoabsorbent assay graft-versus-host human immunodeficiency virus heating, ventilation, and air conditioning invasive aspergillosis lysergic acid diethylamide paracoccidioidomycosis sick-building syndrome solid-organ transplant patients GENERAL PROPERTIES OF FUNGI M olds, yeast and certain related forms such as mushrooms, and toadstools constitute the forms of life known as the fungi. (Mushrooms and toadstools are reproductive structures. The major portion of such fungal forms are located underground). The presence of mold is a common sight on stale bread (without preservatives), rotten fruit, or damp leather goods. Be it fuzzy or powdery, green, black, or white, the growth on so-called moldy food and clothing is familiar to most everyone (Figure 1). Fungi (approximately 100,000 species) are among the most plentiful forms of life. A significant number of species, however, affect humans, lower animals, and plants in various ways. Of these species, at least 30 cause potentially fatal disease in humans, over 35 cause less severe systemic involvement, and about 45 or so species are responsible for more or less minor superficial infections of the skin and mucous membranes. Certain fungi also are known for their production of various types of toxins and enzymes, which have far reaching effects on humans, lower animals, and plant-life. Since fungi, are unable to produce their own food by photosynthesis, as plants do, they exist as parasites on or in other living organisms, or as saprophytes using the nutrients in the dead remains of plant and related organic matter. Structural Features Fungi have well-defined nuclei in their individual cells, and possess certain distinguishing properties that separate them from other microorganisms. Some fungi, such as mushrooms, are large and easily visible to the naked eye. However, most medically important ones are microscopic, and their basic structures require the use of a microscope for a complete identification. A given fungus may be a single cell, or may form growths composed of many This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 11 THE MENACING FUNGI cells known as a mycelium (Figure 1). On the basis of their growth pattern, fungi are divided into two groups: yeasts and molds. Figure 1. The two general forms of fungi are shown in this photograph. The typical mycelial growth of the mold Penicillium can be distinguished from the round, dome-like creamy growth of baker’s yeast, Saccharomyces cerevisiae. Yeasts are single-celled fungi that reproduce by budding (Figure 2) or, in the case of a few species, by a splitting process known as fission. Yeast colonies appear to the naked eye as moist growths on surfaces or on laboratory culture preparations. Molds (also spelled as moulds) are multicellular and form threadlike networks, recognizable as cottony, or fuzzy mycelia (singular, mycelium) mentioned earlier (Figure 1). The threadlike parts of a mycelium (Figure 3) are called hyphae (singular, hypha). The portion of the mycelium concerned with nutrition is known as the vegetative mycelium, while the part that usually projects into the air is known as the aerial or reproductive mycelium. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 12 THE MENACING FUNGI Figure 2. A microscopic view of yeast cells. Buds can be seen on a few of the cells shown. The bar marker represents 20 micrometers. At different temperatures or under different environmental conditions certain fungi may appear as single cells, or may appear as many cells arranged in a definite pattern. This distinction is not always clear, for the two forms may represent different phases of fungal growth. For example, certain pathogens producing disease in human body tissues at 37o C. appear as single cells. However, when grown on laboratory culture preparations maintained at 25o C., the pathogens appear as molds. The capacity of a fungus to exhibit both yeast and mold phases is called dimorphism. Many pathogenic fungi are dimorphic. Reproduction The two major ways in which fungi reproduce are asexual and sexual. These processes are not exclusive and a given fungus may reproduce in one or the other way, or in both ways. Reproductive units (propagules), also generally referred to as spores, are the bases for the asexual growth of most fungi. Multicellular fungi reproduce by the conversion of a reproductive unit into an actively metabolizing vegetative fungus. These units take the form of a variety of spores known as conidia and sporangiospores, depending on the way they are formed. They are formed in a variety of ways, depending on the species. Some spores are formed on the sides or ends of hyphae, and are simply pinched free when they mature (Figure 3). This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 13 THE MENACING FUNGI Figure 3. A scanning electron micrograph showing the long hyphae and the round reproductive units known as microconidia attached to them. Conidia are often given special names that more specifically define the nature of way they are formed or the type of cell producing them. For example, an arthroconidium (also known as an arthrospore) is produced by the conversion of a preexisting, hyphal segment into a conidium that breaks loose from the remaining portion of the mycelium (Figure 4). This type of reproductive unit formation is typical of the respiratory pathogen, Coccidioides immitis. Figure 4. A scanning electron micrograph showing the formation of barrel-shaped arthroconidia (arthrospores) by breaking away from parts (hyphae) of a mycelium. Sporangiospores are formed by the splitting of cells within a sac-like structure called a This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 14 THE MENACING FUNGI sporangium. At the end of the splitting process the sac breaks, thus releasing the newly formed sporangiospores (Figure 5). Figure 5. A scanning micrograph showing the sac-like sporangium and several oval sporangiospores. The microscopic appearance of conidia is one of the major bases for laboratory identification of a fungal species. Most fungi have a sexual reproductive phase. Sexual reproduction involves the same basic process as found with all other forms of life having well-defined nuclei. Such forms of life are called eukaryotes. The end product of the process is the sexual spore . It is formed after the nuclei of two different hyphae have made contact and fused. While the asexual spores described earlier are formed in great numbers, sexual spores are formed only occasionally. The appearance and the development of sexual spores also are used for the identification and classification of fungal species. A Brief Word About Classification The fungi are contained in one of the five recognized biological kingdoms. This kingdom, which consists only of fungi, is further subdivided into phyla and based on the type of sexual reproduction, or lack thereof, within a specific phylum. There are 5 phyla and are known as follows: Zygomycota, Ascomycota, Basidiomycota, Deuteromycota, and Mycophycophyta. The only phylum for which sexual reproduction has not been observed is the Deuteromycota. Fungi pathogenic for humans are found in all phyla with the exception of the Mycophycophyta. Table 1 lists the placement of several fungal pathogens. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 15 THE MENACING FUNGI Table 1. The Phyla of Fungal Pathogens Fungus species Associated Phylum Disease(s) Caused Asperegillus fumigatus and other Aspergillus species Deuteromycota aspergillosis, invasive aspergillosis, allergic bronchopulmonary aspergillosis, aspergilloma Blastomyces dermatitidis Deuteromycota blastomycosis (North American blastomycosis, Gilchrist disease) Candida albicans (and and other Candida species) Ascomycota candidiasis, moniliasis, oral and vaginal thrush, Candida paronychia, bronchomycosis, Candida endocarditis, mycotic vulvovaginitis, candidosis Claviceps purpurea Ascomycota ergot poisoning Coccidioides immitis Deuteromycota coccioidomycois (San Joaquin Valley fever, Valley fever) Cryptococcus neoformans Deuteromycota cryptococcosis, meningoencephalitis, crytococcomas, pulmonary crytococcosis, skin involvement Histoplasma capsulatum Deuteromycota histoplasmosis, (Darling’s disease, reticuloendothelial cytomycosis ) Paracoccidioides brasiliensis Deuteromycota paracoccidiomycosis (South American blastomycosis, Brazilian blastomycosis, Lutz-SplendoreAlmeida’s disease, paracoccidioidal granuloma Penicillium marneffi Ascomycota penicilliosis Classifying Fungal Disease Based on the Site of Infection One of the most common methods of classifying mycoses (fungal diseases), which partly reflects their varying extent of severity and their degree of invasiveness, is based on the location of the infection. According to this type of approach, mycoses are considered to be superficial (cutaneous), subcutaneous , and deep-seated (systemic). Mycoses range from merely annoying to life-threatening. Table 2 lists examples of fungi categorized according to this approach. (It This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 16 THE MENACING FUNGI should be noted that several fungal pathogens involve and attack different body sites.) Superficial and cutaneous mycoses, but not their fungal cause, have been known since the days of Hippocrates in ancient Greece. Both types of disease involve infections of the skin, nails, and hair. In certain cases the mucous membranes also may be infected. Examples of the superficial mycoses mainly include the various types of ringworm, known as the tineas (Figure 6). The protein, keratin, found in the top layers of the skin, nails, and hair is the main target and nutrient for the causative fungi, which are mostly molds. Figure 6. A case of athlete’s foot, also known as tinea pedis. Yeasts such as Candida albicans, which also can attack the skin and nails, can cause infections of the mouth and vaginal areas known as oral and vaginal thrush, respectively. Oral Candida infections (Figure 7), especially those involving the esophagus, are considered as indicator diseases in cases of human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS). This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 17 THE MENACING FUNGI Figure 7. A case of oral candidiasis, also known as oral thrush. Table 2. Examples of Fungus Infections and/or Diseases Fungus Infection and/or Disease Cause Category various types of tinea (fungus infections of the nails, skin and hair) a number of mold species, and yeasts such as Candida species superficial mycosis blastomycosis dimorphic fungus deep-seated mycosis candidiasis yeast superficial and subcutaneous mycoses chromoblastomycosis mold subcutaneous mycosis coccidioidomycosis dimorphic fungus deep-seated mycosis cryptococcosis yeast deep-seated mycosis histoplasmosis dimorphic fungus deep-seated mycosis invasive aspergillosis mold deep-seated mycosis paracoccidioidomycosis dimorphic fungus deep-seated mycosis penicilliosis mold deep-seated mycosis This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 18 THE MENACING FUNGI sporotrichosis mold subcutaneous mycosis The subcutaneous mycoses can be quite destructive and disfiguring for victims. Such infections attack the upper skin layers, bone, tendons, and muscles. They include sporotrichosis, and chromoblastomycosis. Unfortunately some of these infections can develop into the last category, namely systemic mycoses. Systemic mycoses, also known as deep-seated mycoses, are caused by either primary or opportunistic infectious fungi. These fungi can be divided into two categories, primary pathogens , which include the highly virulent Coccidioides immitis and Histoplasma capsulatum, and opportunistic pathogens such as Aspergillus fumigatus and Candida albicans. Primary pathogens can affect otherwise healthy individuals with normal immune systems, while opportunistic pathogens produce illness by taking advantage of debilitated or immunocompromised hosts. The majority of human mycoses are caused by opportunistic fungi. Initially, many of the deep-seated infections are asymptomatic or mild in their effects, infecting the sinuses and other portions of the respiratory and related body systems. Left untreated several of these mycoses can become systemic as well as lethal. The body organs and systems that can be involved include the lymphatic system, liver, spleen, kidneys, and the components of the central nervous system. These infections occur in fairly large sections of human populations where the causative fungi are endemic. Opportunistic fungi are not restricted to any specific geographic area and are found worldwide. The three genera of fungi most frequently found as severe agents of opportunistic infections are Aspergillus, Candida, and Cryptococcus. It should be noted that in recent years unusual opportunistic fungal pathogens have also emerged and thereby have increased the need by health care personnel for a greater awareness of the risk of immunocompromised as well as immunocompetent patients developing severe forms of mycotic infections. Several factors are known to contribute to the increasing number of opportunistic fungal infections. These include: 1) immune defects and/or deficiencies such as acquired immune deficiency syndrome (AIDS), 2) the inappropriate and/or prolonged use of antibiotics, 3) the use of immunosuppressive drugs, 4) endocrine disorders, 5) malignancies, 6) surgical procedures, 7) organs transplants, 8) indwelling catheters or shunts, and 9) various other procedures currently used in medicine. ANTI-FUNGAL AGENTS USED IN TREATMENT T he drugs used to treat fungal infections work differently from those used for bacterial infections, and belong to different chemical groups. Amphotericin B belongs to the oldest class of antifungal agents, the polyene macrolides. This antimycotic agent binds to ergosterol, a major component of the plasma membrane of fungal cells. This binding creates channels in the fungal membrane that increase permeability and cause cell death through leakage of essential nutrients. Azole antimycotics interfere with ergosterol formation. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 19 THE MENACING FUNGI Amphotericin B deoxycholate (AmB-d) has been the agent-of-choice for treatment of patients who are at high risk for or who have documented invasive fungal infections. In attempts to decrease the incidence of drug infusion-related and renal toxicities, bench-to-bedside studies were used to develop other formulations and approaches to the use of amphotericin B for clinical use. Through such investigations three commercially available lipid formulations were developed which have been shown to be significantly less nephrotoxic than AmB-d. The resulting compounds were: 1) liposomal amphotericin B, 2) amphotericin B lipid complex, and 3) amphotericin B colloidal dispersion (ABCD). In addition, a lower incidence of infusionrelated toxicity was found with the use of liposomal amphotericin B. In reported clinical trials with ABCD, the antimycotic agent was shown to have an excellent renal safety profile, even when used to treat patients with preexisting renal insufficiency. In addition to the lipid formulations of amphotericin B, newer antimycotic agents including triazoles such as voricinzole, posaconzole, and ravuconazole, and the echinocandins such as pofungin, micafungin and anidulofungin have provided more treatment choices for lifethreatening invasive fungal infections. The echinocandins interfere with formation of the outermost part of fungal cell, the cell wall. Other approaches also are being studied which have the potential of reducing drug toxicity and increasing drug effectiveness. One of these is the use of an echinocandin-triazole combination in the treatment of invasive aspergillosis. The combination may result in the inhibition of the formation of both the cell wall and cell membrane of A. fumigatus. Additional studies are needed to determine the effectiveness of drug combinations such as these. Table 3 lists several examples of anti-fungal (anti-mycotic) drugs used in the treatment of serious fungus infections, together with their mechanisms of action. Table 3. Examples of Anti-fungal Agents Used in the Treatment of Fungal Infections Anti-fungal Agent Class Mechanism of Action amphotericin B polyene binds to sterols in fungal plasma (cell) membranes, making such membranes excessively permeable and killing the cells a caspofungin echinocandin interferes with fungal cell wall formation clotrimazole imidazole primarily interfere with sterol synthesis in fungi flucytosine nucleoside analogue inhibits DNA and RNA synthesis fluconazole triazole same as for clotrimazole This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 20 THE MENACING FUNGI itraconazole triazole same as for clotrimazole ketoconazole imiddazole same as for clotrimazole miconazole imidazole same as for clotrimazole a Sterols are high molecular weight alcohol compounds related to fats, and common components of fungal and other plasma (cell) membranes. VACCINES C urrently there are no vaccines available for the primary fungal pathogens or any of the opportunistic fungal pathogens. However, various preparations are under study. THE PRIMARY FUNGAL PATHOGENS Blastomycosis B lastomycosis is a deep-seated mycosis caused by the fungus Blastomyces dermatitidis. This disease usually starts as a respiratory infection and spreads with pulmonary, bone, and skin involvement predominating. Geographic Distribution This disease occurs sporadically in African countries such as South Africa, Tanzania, and Zaire, Canada, central and southeastern United States, India, Israel, and Saudi Arabia. Habitat The usual habitat of Blastomyces dermatitidis is largely moist soil and wooded areas along waterways and undisturbed places containing organic debris, such as porches or wood sheds. Culture and Microscopic Features Blastomyces dermatitidis a dimorphic fungus. In culture at room temperature, the fungus grows slowly and forms a white cottony mycelium consisting of hyphae bearing spherical or ovoid conidia measuring 2 to 10 micrometers in diameter. The conidia are situated at the end of hyphae or on short stalk-like structures, known as conidiophores (Figure 8). This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 21 THE MENACING FUNGI Figure 8. A microscopic view of Blastomyces dermatitidis hyphae and spherical to ovoid conidia (spores). In tissues and laboratory cultures incubated at 37 o C., the fungus takes the form of large spherical or oval cells ranging in size from 8 to 15 micrometers (Figure 9). These cells reproduce by budding. Figure 9. A microscopic view of the yeast form of B. dermatitidis. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 22 THE MENACING FUNGI Transmission Humans and other mammals such as dogs acquire blastomycosis by inhaling conidia from mycelia growing in soil or from various articles contaminated by conidia. Infections are sporadic and can occur with all ages. However, there appears to be a higher incidence with individuals in the age range of 30 to 50. There is no evidence of person-to-person transmission. Cases of the disease have been reported in a horse, a captive lion, and sea lion. Clinical States Clinical manifestations of the disease have been classified into three general groups: 1. pulmonary blastomycosis; 2. disseminated blastomycosis; 3. cutaneous blastomycosis. Table 4 lists these conditions together with their distinguishing features. Table 4. The Clinical Manifestations of Blastomycosis Clinical Manifestation Distinguishing Features pulmonary blastomycosis usually begins as a mild respiratory infection which progresses with dry cough, pleuritic pain, hoarseness, and low grade fever; chest X-ray examination in early stages shows hilar shadow widening or disease process suggestive of tuberculosis or carcinoma; disease progresses to death, if untreated Signs and Symptoms: as disease progress, sputum becomes purulent and blood-streaked; fever, dyspnea, loss of weight and strength, night sweats disseminated blastomycosis involves the skin, oronasal mucosa, and subcutanous tissues, and the respiratory, musculoskeletal, urogenital, and central nervous systems; the gastrointestinal system is rarely involved; Signs and Systems: are determined by body system affected; destructive lesions occur in vertebrae, tibia and femur; This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 23 THE MENACING FUNGI musculoskeletal system - pain and loss of function, takes the form of osteomyelitis, inflammation of membranes surrounding bones (periostitis) and septic arthritis; urogenital system - painful urination, and the presence of blood and pus in the urine. cutaneous blastomycosis a wide variety of skin lesions may occur; ulcerated, crusted lesions appear resulting from an extension of lesions from underlying bone and/or subcutaneous lesions, the introduction of the pathogen by direct inoculation of the skin; these lesions are secondary to the lung infection; Laboratory and Related Aspects of Diagnosis A clinical diagnosis of blastomycosis is presumptive and must be supported by a laboratory diagnosis. It is necessary to demonstrate the fungus in clinical specimens such as pus, sputum, or biopsy materials, and to isolate it in culture. Blood (serologic) tests are not useful. Treatment The drug-of-choice is itraconazole. However, amphotericin B is used with seriously ill individuals and in cases of the presence of brain lesions. Prevention and Control The most obvious preventative measure in the prevention of PCM infection is the avoiding of contact with soil contaminated objects possibly containing conidia and/or mycelial fragments in endemic areas. Disinfection of all contaminated articles is an important preventative measure. COCCIDIOIDOMYCOSIS C occidioidmycosis, also known as San Joaquin Valley fever or simply Valley fever, is a mycotic disease caused by Coccidioides immitis and the newly proposed related species C. posadasii. This disease is considered to be a reemerging disease as a result of the dramatic increase in cases during the 1990’s. Major outbreaks occurred in southern California in 1977, and late 1991 through 1994. A significant increase in cases also occurred in 2003. Coccidioidomycosis also has long been recognized as a travel-related mycosis associated with visits to endemic areas in southern California, Arizona, and other neighboring states. Sporadic cases have been reported in areas where the disease is not endemic. Adding to the importance of C. immitis is its being added to the growing list of bioterrorism agents. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 24 THE MENACING FUNGI Habitat Coccidioides immitis grows in soil in areas of low rainfall, high summer temperatures, and moderate winter temperatures. The fungus is endemic to the South-western United States including the San Joaquin Valley of California and southern portions of Arizona, northern Mexico, parts of Central America such as Guatemala, and Honduras, and in several countries of South America including Venezuela, Columbia, Paraguay, and Argentina. Coccidioidomycosis is also endemic in Utah, Nevada, New Mexico, and Texas. Culture and Microscopic Properties At room temperature, a C. immitis culture grows as a mycelium (Figure 10) composed of hyphae, which form typical barrel-shaped arthroconidia (conidia). The conidia are highly infectious (Figures 4 and 11). In the body (in vivo), C. immitis exists as large spherules ranging in size from 30 to 200 micrometers, and containing numerous small endospores (Figure 12). Spherules generally average from 30 to 60 micrometers in diameter, while endospores measure about 2 to 5 micrometers in diameter. Figure 10. The cottony mycelium of C. immitis. Variations in size and color do occur. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 25 THE MENACING FUNGI Figure 11. A microscopic view of stained C. immitis arthrospores. Note the barrel-shape of the conidia and the spaces between the conidia. Transmission Humans and other certain other mammals acquire Coccidioidomycosis generally by the inhalation of C. immitis arthroconidia (spores). The mycelia of the fungus give rise to these infectious spores (arthroconidia), which become aerosolized when the soil is disturbed. Outbreaks of the disease often occur after dust storms, earthquakes, and major soil excavations. In Southern California factors considered to contribute to making the spores more airborne than usual include wildfires that destroy vegetation thereby exposing soil, followed by high winds. Rare outbreaks of coccidioidomycosis have been reported among anthropologists, and archaeologists digging in ruins located in endemic areas. In addition, cases of the disease have occurred among farmers, construction workers, and ranchers engaged in various types of activities and exposed to spore-containing soil and dust. The risk of infection in such situations is quite high. Coccidioidomycosis is one of the most commonly reported infections among travelers. Such travel-associated mycoses are the result of a wide range of recreational activities, many of which involve long-recognized risk factors for the infection. A number of lower warm-blooded animals can be victims of coccidioidomycosis, and acquire infection through the inhalation of conidia-bearing dust particles. Cattle, dogs, horses, sheep and certain wild rodents are susceptible to infection. Birds generally are not susceptible to the disease. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 26 THE MENACING FUNGI Life Cycle The life cycle of C. immitis is somewhat more complicated than most other systemic mycoses. It involves the development of a hyphae, mycelium, arthroconidia, and spherules, and endospores. In soil, or on routine culture media preparations for the isolation, the fungus produces a mycelium with characteristic branching hyphae and arthroconidia that usually, but not invariably, form in alternate hyphal cells (Figures 4 and 11). As the arthroconidia mature, the hyphal cells between them disintegrate, and the arthroconidia are released as single structures. These conidia are barrel-shaped (Figure 11), bear fragments of the cell material from the disrupted adjacent hyphal cells, and measure about 3 by 6 micrometers. In tissue or on specially prepared media, the arthroconidia transform into spherical, large endospore-containing spherules (Figure 12). These spherules range in size and can reach 200 micrometers in diameter. Upon maturity, the spherules rupture to release their endospores, which may in turn develop into spherules. Figure 13 provides a general view of the life cycle of C. immitis. Figure 12. A stained tissue specimen containing a typical endospore-containing C. immitis spherule. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 27 THE MENACING FUNGI Mycelium Development Soil Cycle Arthroconidia Endospores Endospore Stage Immature spherules Parasitic Cycle In Host Segmentation Spherule Development Figure 13. The life cycle of C. immitis. The soil cycle and the host parasitic cycle, which takes place in the human, are shown. Pathogenesis Coccidioidomycosis is usually initiated when aerosolized arthroconidia are inhaled. Such conidia are small enough to reach the lower respiratory tract, including the alveolar air spaces. Upon gaining entrance to this body area, the interaction of host defenses and various fungal factors, determines the outcome of the infection. A combined pyogenic and chronic inflammatory response often develops. In a small percentage of cases, the spherules rupture and the infectious process spreads and produces the progressive form of the disease described in a later section. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 28 THE MENACING FUNGI Since most cases of the mycosis are self-limiting and produce minimal symptoms, the only evidence of infection is the development of an immune response. This response usually takes the form of a conversion of the individual’s negative skin test response to a positive delayed type skin reaction and the production of specific antibodies (immunoglobulins) to C. immitis proteins. Individuals At Risk This group includes HIV-infected persons, the elderly, diabetics, pregnant women in their third trimester, and a variety of ethnic groups including African-American, and Filipino-Americans. Both localized pneumonia and disseminated (spreading) infection are usually observed in those individuals with CD4+ T lymphocyte counts less than 250 cells / microliter. The disseminated form of coccidioidomycosis also is more likely to occur among persons with blood group B and individuals with genes that code for certain histocompatibility (tissue) antigens. The histocompatibility antigens are also known as the human leukocyte antigen (HLA) complex. Clinical States The severity of coccidioidomycosis varies from an inapparent upper respiratory infection to a disseminated (spreading) fatal disease, and is only symptomatic in approximately 40 percent of cases. Most patients experience the signs and symptoms of a flu-like illness. The two most common clinical presentations of coccidioidomycosis are disseminated disease and meningitis. Asymptomatic infections are generally detected only with the aid of positive skin tests showing a hypersensitivity to coccidioidin or spherulin. These skin testing materials are specific proteins extracted from C. immitis. It should be noted that the disease is not contagious. Clinical manifestations of the disease have been classified into three general groups: 1. initial (primary) pulmonary coccidioidomycosis; 2. pulmonary complications; 3. extrapulmonary disease. Table 5 lists these conditions together with their distinguishing features. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 29 THE MENACING FUNGI Table 5. Coccidioidomycosis Clinical Manifestations Clinical Manifestation Distinguishing Features initial (primary or acute) pulmonary coccidioidomycosis usually self-limiting and is symptomatic in approximately 40 percent of cases; usually begins as a respiratory infection after inhaling airborne C. immitis arthrospores; incubation period generally varies between 7 to 28 days. a Signs and Symptoms: backache, fatigue, fever, cough, headache, and muscle and joint aches and pains; a generalized macular, erythematous rash (small red spots) may appear in about 10 percent of patients. (The presence of a rash and associated joint pains were, in fact responsible for the name “desert rheumatism” given to the disease by some of the early victims.) pulmonary complications Signs and Symptoms: lesions are confined to the lungs, giving pulmonary symptoms of varying severity, and sometimes result in cavitation; chest X-rays typically show pulmonary infiltrates, which may be single or multiple, segmental, or lobar - such X-rays also may show a widening of hilar shadows (hilar adenopathy). frequent pleuritic pains, which may be severe and appear so suddenly as to simulate a traumatic rib fracture, heart attack, an acute inflammation of sac enclosing the heart, or a gall bladder attack (pain associated with respiration may be accompanied by substernal pain or pressure, and when the latter is severe it may interfere with swallowing). EXAMPLES OF COMPLICATIONS a.) Chronic pulmonary cavitation: most frequent complication of primary coccidioidomycosis; occurs in approximately 2 to 8 percent of symptomatic infections; the cavity usually, but not always, has a thin wall with little surrounding reaction, and is solitary; this complication may be almost without symptoms, and discovered only accidentally during a routine X-ray examination; cavities may not respond to chemotherapy, and progressive enlargement of a chronic cavity often is related to secondary bacterial infection. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 30 THE MENACING FUNGI Signs and Symptoms: cough, slight chest pain, sputum production, and hemoptysis; the cavity may persist for several years without the disease spreading to other body areas; b) Coccidioidoma: usually represents a healed or arrested pneumonitis or granuloma; such conditions usually remain stable, but may contain some calcium; Signs and Symptoms: patients are asymptomatic, and the condition does not represent a hazard of probable reactivation; the lesion however, may present a medical problem in that it may be difficult to differentiate it from a carcinoma. c) Bronchiectasis and pulmonary fibrosis: occasional complications of primary coccidioidomycosis; Signs and Symptoms: empyema, pneumothorax, and hydropneumothorax may complicate the primary form of coccidioidomycosis, and may be related to a spreading of the initial lesion. d) Chronic coccidiodomycosis: most frequently observed in diabetics and in immunocompromised patients. Extrapulmonary Disease as a rule, primary infection usually ends in recovery, however, in a small percentage of cases, the infection spreads from the lungs to produce the progressive form of coccidioidomycosis; this form of disseminated disease occurs most often in non-white individuals, particularly African- and Filipino-Americans, males, pregnant women, and immunocompromised persons; Disseminated (spreading) infections may occur promptly and rapidly by the circulatory spreading of endospores (Figure 7) from the lungs to other organs; the rapidity of spreading spores appears to be related to the failure of the immune system to stop the process; in the progressive or secondary form (also known as coccidioidal granuoma); the progression of this form of coccidioidomycosis may be slow or rapid, or the patient may recover, except in cases of acute wide spreading of the spores and meningitis. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 31 THE MENACING FUNGI Signs and Symptoms: disease process spreads to the skin, subcutaneous tissues, the bones, meninges, and internal organs; skin lesions resemble those of certain other deepseated mycoses, while in other parts of the body they resemble those of tuberculosis; The signs and symptoms are site-specific and include wartlike nodules, papules, and ulcers involving the skin, headache, and arthritic pains and swelling in the joints, especially in the knees and/or ankles; multiple painful lesions also may develop in the skull, hands, feet, spine, or long bones; the course of the disease is marked by remissions and exacerbations; unfortunately, the mortality is high. a A massive exposure to contaminated soil or to the careless handling of positive C. immitis cultures in a laboratory is followed usually by a shorter incubation period. C. immitis as well as Histoplasma capsulatum are among the know causes of communityacquired pneumonia (CAP). HIV-Infected Patients As indicated earlier, immunocompromised individuals are at a much higher risk for severe forms of coccidioidomycosis. Pulmonary infection in such patients may develop into one of several complications including pulmonary nodules, thin-walled cavities, progressive pneumonia, pyopneumothorax, and bronchopleural fistula. Disease susceptibility to coccidioidomycosis is highest in HIV-infected persons who have a severe depletion in their CD4+ lymphocytes. This condition corresponds to a laboratory finding of <200 CD4+ cell/ cubic millimeters of blood. Cocccidioidomycosis should be suspected in such individuals if they have lived or traveled in an endemic area for the disease, or who may have otherwise been exposed to the disease agent. Unfortunately, the prognosis for individuals with a low CD4+ count is poor. The progression of the disease is rapid and inevitably fatal. Signs and Symptoms: HIV-infected patients commonly experience a cough, dyspnea, and fever. Skin lesions and meningitis are uncommon. Chest X-rays typically show the diffuse reticulonodular pattern of extensive involvement as well as focal pulmonary infiltrates similar to those found with bacterial pneumonias. Solid-Organ Transplant Recipients Recipients of solid-organ transplants also are at an increased risk of developing disseminated coccidioidomycosis. This form of the disease was first reported among solid-organ transplant recipients (SOTRs) in the late 1960’s. Since this time it has been increasingly recognized among This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 32 THE MENACING FUNGI SOTRs, with the majority of infections occurring in the first year after transplantation. The mortality rate associated with the disseminated disease has been reported to be as high as 72 percent among such patients. The possible sources of C. immitis in SOTRs is believed to be donor organs. In 2003, P.W. Wright reported two cases of disseminated coccidioidomycosis in SOTRs that resulted from the transmission of C. immitis from a single organ donor with unrecognized active coccidioidomycosis at the time of his death. Laboratory and Related Aspects of Diagnosis Radiologic studies such as chest X-rays, and bone scans, are of value in determining the extent and severity of the disease process, but unfortunately cannot distinguish coccidioidomycosis from other pulmonary diseases. A definitive diagnosis requires laboratory procedures including the microscopic examination of body fluids and/or tissue specimens, culture, and immunoserologic evidence. The latter approach involves tests to detect specific antibodies (the immunoglobulins IgG and IgM) against C. immitis antigens, and skin testing procedures. The isolation and culture on appropriate laboratory culture media and demonstrating the presence of arthroconidia (Figure 11) as described earlier is specific, but requires a significant long incubation period for results. The finding of typical spherules (Figure 12) in sputum, and/or tissues biopsy materials also is diagnostic and much faster than the isolation approach. A commercially available deoxyribonucleic acid (DNA) probe also can be used to identify isolated cultures of the fungus. Serologic diagnosis is of value showing the presence of specific antibodies against C. immitis antigens. Several antibody (immunoglobulin) responses are particularly diagnostic. The tests used include the immunodiffusion test, enzyme-linked immunoabsorbent assay (ELISA), complement fixation test, and the polymerase chain reaction (PCR). Each procedure has distinct advantages and disadvantages. The PCR assay is the most rapid of the ones listed. Skin Tests. Skin tests are performed in a manner similar to that used with the tuberculin skin test. A filtered extract of a C. immitis culture, known as coccidioidin, is commonly used for testing purposes and is injected intradermally. Spherulin, an extract of the spherule phase of the fungus also has been used for skin testing. Skin tests measure the delayed type hypersensitivity response of the individual to C. immitis antigens. The results of the procedure are usually read 48 hours after the injection of the skin testing material. It should be noted that it takes approximately 3 weeks after exposure to C. immitis to develop a positive skin test. A positive reaction indicates previous exposure to the fungus, or in some cases the result of repeated testing. Generally, individuals with a normal positive skin test are immune to a second attack of the fungus. A negative skin test may mean several things including: 1) the test was performed too early in the disease process, 2) a case of disseminated coccidioidomycosis exists in which the individuals immune response has been impaired; 3) the current illness of the patient is not the disease being tested for, 4) the individual being tested is immunocompromised and the immune system has This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 33 THE MENACING FUNGI been impaired. While skin tests have limited diagnostic value, they can be useful in epidemiologic investigations and in evaluations of individuals exposed to C. immitis after previously producing negative skin test reactions. Treatment The common form of coccidioidomycosis is a self-limited type of infection and other than supportive care usually does not require antimycotic therapy. Treatment is recommended in certain cavitary forms of the disease, and is required for disseminated coccidioidomycosis. Amphotericin B, the first effective antimycotic used for treatment, remains the drug standard by which all newer preparations are judged. It is not the drug-of-choice for long term use largely because of its toxicity. Amphotericin is administered intravenously for two to three months for the treatment of both localized and disseminated forms of the disease. Newer antimycotics such as fluconazole, itraconazole, and ketoconzole provide many of the same benefits found with amphotericin B and are significantly less toxic. Table 6 lists examples of drugs used in treatment together with dosages and associated side-effects. These newer preparations are available for oral administration. Table 6. Examples of Drugs Used in the Treatment of Coccidioidomycosis Drug Dosage Noted Side -Effects amphotericin B 0.5-0.7mg/kg/day fever; nausea, vomiting, kidney toxicity, potassium and magnesium depletion fluconazole 400-600 mg/day high relapse rate itraconazole 200 mg/twice per day poor absorption of the drug, drug interactions, and relapse rate ketoconazole 400 mg/day nausea, vomiting, liver toxicity, adrenal suppression, abnormal breast development in males, no absorption in patients with no hydrochloric acid in their stomachs, drug interactions, and high relapse rates Since most of the newer drugs inhibit fungal growth (fungistatic) rather than kill the disease causing fungus (fungicidal), relapses are common occurrences. In addition, the optimal time period of therapy is not known. The information currently available on relapse situations points to the continuation of treatment for at least six months after fever, and a significant reduction and/or elimination of the signs and symptoms have occurred. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 34 THE MENACING FUNGI Several drugs for treatment are under study. These include new formulations of amphotericin B and the azoles. Among these are the azoles DO870, which is effective against fluconazoleresistant fungi, and nikomycin A, which inhibits fungal growth not only of C. immitis, but other dimorphic pathogens as well. In 2004, T.T. Kuberski et al, reported the use of the immune-modulating (strengthening) agent interferon-gamma as an adjunct to conventional antifungal therapy for a patient with disseminated C. immitis infection and respiratory failure. The addition of the agent resulted in the improvement of the patient’s condition and subsequent discharge from the hospital. Surgery, in the form of pulmonary resection, while being required less often, continues to play a role in the management of hemoptysis and extensive pulmonary cavitation. Other invasive procedures may be used in managing empyema, or persistent bronchopleural fistula. Potential organ transplant patients should receive antifungal therapy prior to their respective operations. Therapy should also be given as soon as possible to patients experiencing acute organ rejection, and to HIV-infected pregnant women who have previously experienced C. immitis infection. Prevention and Control The most obvious preventative measure in the prevention of C. immitis infection is the avoiding of contact with dusty soil and/or body fluids and tissues possibly containing arthroconidia, spherules, or endospores. The planting of grass and other types of plants, as well as paving roads in highly populated endemic areas are valuable preventative measures. Periodic skin testing and the testing for IgG (antibodies) against C. immitis at about six-month intervals may provide the basis for an early detection of the disease. The use of oral azoles as a preventative measure is not recommended, and should be used only in cases of serious complications. The use of these drugs is different for HIV-infected persons. Once started, oral azole treatment in such cases must be continued for the lifetime of the individual. HISTOPLASMOSIS H istoplasmosis, also known as Darling’s disease is caused by the dimorphic fungus Histoplasma capsulatum. The name of this pathogen was suggested by S.T. Darling in 1906 and was based on the histological appearance of yeast-like cells in the macrophages of a patient. The Causative Agents There are three known varieties of H. capsulatum, namely H. capsulatum variety capsulatum, H. capsulatum variety duboissi, and H. capsulatum variety farciminosim. Each of these varieties This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 35 THE MENACING FUNGI produce a distinctive histoplasmosis syndrome. Only the H. capsulatum variety capsulatum will be principally considered in this course. H. capsulatum is recognized as an intracellular pathogen. This fungus can involve the lymphatic system, spleen, liver, adrenals, kidneys, skin, and the central nervous system. Habitat H. capsulatum has been isolated from soil containing high nitrogen concentrations, especially those relating to the fecal droppings of chickens and birds such as blackbirds which include starlings, grackles, red-winged blackbirds, and cowbirds, and those of bats. Outbreaks of pulmonary histoplasmosis have been linked to exposure to these H. capsulatum reservoirs in their natural settings as well as to materials contaminated by the fecal material. Because of their high body temperatures birds are not infected with H. capsulatum, however, their fecal droppings provide a rich source of nutrients and a favorable growth environment. The habitats of pigeons, and poultry houses with dirt floors, have been found to be heavily contaminated with H. capsulatum. Determining whether or not soil and other types of materials are contaminated with this fungus requires the collection of specimens and the subsequent culturing on appropriate nutrient media by trained laboratory personnel. Bats on the other hand, because of their lower body temperature, can become infected and carry the fungus to other locations. Other warm-blooded animals also can become infected with H. capsulatum. These include bears, cats, dogs, mice, opossums, raccoons, rats, and skunks. Although histoplasmosis is found throughout the world, it is principally endemic along the Ohio, Mississippi, and St. Lawrence rivers. The disease agent also has been found in other areas of the United States. Wet or dry seasons do not appear to have an association with infections. Culture and Microscopic Features In soil and on laboratory culture media incubated at 25o C. (room temperature) H. capsulatum produces a typical white to brown mycelium. Microscopically, a mycelium consists of branching hyphae that form small single conidia (microconidia) and larger spores with spiny or fingerlike structures on their surfaces. The large spores are distinctive and are referred to as tuberculated macroconidia (Figure 14). This form of the fungus can be converted to its yeast form by cultivation at 37o C. (body temperature). The microconidia are infectious and cultures should be handled with strict biosafety precautions. It should be noted that the mycelia of H. capsulatum, as well as other pathogenic fungi do not appear overnight. In most cases at least three to four weeks are required for best results. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 36 THE MENACING FUNGI Figure 14. A microscopic view of a tuberculated macroconidium at the end of a branching hypha of H. capsulatum. After the microconidia are inhaled by an individual, they undergo a sequence of changes that transform them into yeast cells. These transformed cells are generally found in tissue macrophages, however, they can also be found extracellularly. Life Cycle The life cycle of H. capsulatum involves the development of hyphae, a mycelium, micro- and macro-conidia, and yeast cells. In soil, or on routine culture media preparations for the isolation, the fungus produces a mycelium with characteristic branching hyphae and micro- and macroconidia when incubated at room temperature. The yeast phase of the cycle occurs in tissue or when cultures are incubated at body temperature (37o C). Inhaled microconidia are engulfed by macrophages and are transformed into oval to spherical-shaped yeast cells. Transmission Histoplasmosis follows the inhalation of small conidia into the lungs, where they germinate and are transformed into budding yeast cells. The disease is not contagious since it cannot be transmitted from an infected individual or lower animal to someone else. H. capsulatum can be carried on the wings, feet, and beaks of birds and thereby bring about the contamination of soil under bird roosting sites, or manure accumulations inside or outside of building. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 37 THE MENACING FUNGI Exposure Risks Histoplasmosis also is known as cave sickness or speleonosis, largely because some of its victims have been spelunkers (cave explorers). Other victims of the disease tend to be outdoor types such as farmers, construction workers, gardeners, roofers, chimney sweeps, heating and/or air conditioning service personnel, individuals involved with the restoration of historic or abandoned buildings, and pest control workers. Pathogenesis Histoplasmosis usually starts when microconidia of H. capsulatum growing in soil or on material contaminated with infectious bird or bat fecal matter is aerosolized. Upon gaining entrance to this body area, the interaction of host defenses and various fungal factors, determines the outcome of the infection. The inhaled microconidia are engulfed by macrophages of the body where the fungal cells undergo as sequence of structural changes and become yeast cells. These cellular events are crucial to both natural and acquired resistance of the host to H. capsulatum. The yeast cells of this fungus survive in host polymorphonuclear leukocytes and grow and reproduce in circulating mononuclear phagocytes. Progressive spreading of the infection involves reticuloendothelial host cells such as those found in the lymph nodes, liver, and spleen. Clinical States Histoplasmosis can present a variety of clinical manifestations, which may be grouped according to the following categories: 1. body location: pulmonary, extrapulmonary, or disseminated; 2. duration of infection: acute, subacute, or chronic; 3. pattern of infection: primary versus reactivation. Table 7 lists examples of these forms of H. capsulatum disease according to body location and duration of infection, together with descriptions of the conditions. Primary pulmonary infections may develop in healthy, immunocompetent hosts exposed to a massive concentration of H. capsulatum conidia, while elderly individuals, and immunocompromised patients, may experience a reactivation of primary histoplasmosis. Cases of reactivated disease must be distinguished from other fungus infections, tuberculosis, and various types of cancers. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 38 THE MENACING FUNGI Table 7. Clinical Manifestations of H. capsulatum Infection Clinical Manifestation Features of the Condition primary pulmonary infections may be asymptomatic, subclinical, or a self-limited pulmonary disease of varying degrees of severity that leaves multiple areas of calcification (small calcified foci) in the lungs and lymph nodes of the chest. Chronic cavitary disease: may result from a small percentage of primary pulmonary cases and can worsen with time, especially if the condition is not diagnosed and treated appropriately; resembles tuberculosis. Disseminated disease: the most severe and rarest form of histoplasmosis. primary acute histoplasmosis the vast majority of individuals are asymptomatic. the only evidence of exposure and of the asymptomatic infection is a positive skin test, which uses an antigen prepared from the mycelial phase of H. capsulatum called histoplasmin. Signs and Symptoms: appear within 3 to 17 days, and generally suggest a flu-like illness, and include fever, a dry or nonproductive cough, headache, chest pain, shortness of breath, chills, and joint and muscle aches and pains. disseminated histoplasmosis involves the reticuloendothelial cells of the body, such as those found in the liver, spleen, and lymph nodes. Yeast cells are present intracellularly. Signs and Symptoms: irregular fevers, loss of weight, a reduction in the number of leukocytes, ulcerating lesions in the nose and mouth, and enlargements of the spleen, liver, and lymph nodes are evident. cavitary histoplasmosis occurs predominantly in adults; some cases may represent reactivation of a primary lung lesion, or an uninterrupted progression of a pulmonary lesion. In this form of histoplasmosis, the disease process has spread and if the severity of the condition increases, any of the usual manifestations of disseminated histoplasmosis listed earlier may appear. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 39 THE MENACING FUNGI Signs and Symptoms: closely resemble those found with tuberculosis, and include productive cough, low-grade fever, occasional hemoptysis, and radiological findings of pulmonary cavitation. extrapulmonary histoplasmosis exposure to massive numbers of conidia results in a rapid fatal end. Signs and Symptoms: the pulmonary manifestations may be less prominent and the signs and symptoms listed for earlier for the primary acute form of histoplasmosis characterize the condition; any of the manifestations may predominate and the illness then appears as carditis, meningitis, adrenal gland or liver insufficiency, or as large solitary or multiple lesions in various parts of the gastrointestinal system. When intestinal lesions predominate, it is possible that the primary lesions may have been in the intestinal lymphatics, and that infection followed ingestion rather than inhalation of H. capsulatum microconidia. Laboratory and Related Aspects of Diagnosis Radiologic studies, which include chest X-rays, and body scans, are of value in determining the extent and severity of the disease process, but unfortunately cannot distinguish histoplasmosis from other fungus-caused pulmonary diseases, tuberculosis, or various forms of cancers. A definitive diagnosis requires laboratory procedures including the microscopic examination of sputum, peripheral blood, and aspirated material from lymph nodes and bone marrow. Culture isolation and immunoserologic evidence (blood tests) also are important to diagnosis. The latter approach involves tests to detect specific antibodies (the immunoglobulins: IgA, IgE, IgG and IgM) against H. capsulatum antigens, and skin testing. Several specific immunologic tests are used. These include immunodiffusion, complement fixation, and latex agglutination. A PCR assay, which is one of the most rapid procedures, also is available. The isolation of H. capsulatum on appropriate laboratory culture media and demonstrating the presence of the tuberculated macroconidia (Figure 9) as described earlier is specific, but requires a significant long incubation period for results. The finding of the yeast cell phase in sputum, and/or tissues biopsy materials also is diagnostic and much faster than the isolation approach. Skin Tests. Skin tests are performed in a manner similar to that used with the tuberculin skin test. A filtered extract of a H. capsulatum mycelial culture, known as histoplasmin is used for testing purposes and is injected subcutaneously. Skin tests measure the delayed type hypersensitivity response of the individual to H. capsulatum antigens. The results of the procedure are usually read 48 hours after the injection of the skin This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 40 THE MENACING FUNGI testing material. It should be noted that it takes approximately 3 weeks after exposure to the fungal pathogen in order to develop a positive skin test. A positive reaction indicates previous exposure (infection) to the fungus. Treatment In its common form, histoplasmosis is an acute, self-limited infection that generally does not require therapy other than supportive care. In some cavitary forms of the disease therapy is recommended with amphotericin B. Some of the newer antimycotic drugs mentioned earlier for the treatment of coccidioidomycosis may prove useful as experience with them develops. Amphotericin B is currently considered to be the first-line treatment for patients with severe forms of disseminated histoplasmosis. In other cases, itraconzole may be used. The advantages of itraconzole therapy over amphotericin B include lower toxicity, and the possibility of oral administration. Prevention and Control The most obvious measure for the prevention of H. capsulatum infection is avoiding contact with areas and/or objects that may harbor the fungus such as bird or bat fecal matter. Other recommended preventative measures include: 1) posting of signs warning of health risks, 2) preventing the accumulations of bat and/or bird fecal matter, which would include areas such as bird roosts, attics, and related locations, 3) removing and excluding bats and/or birds from buildings, (this involves the closure and sealing of any and all possible entrances), 4) carefully wetting areas from which infectious material is to be removed before any removal is attempted, 5) using industrial vacuum systems for removal of bat and/or bird droppings, 6) collecting infectious material in secure containers for immediate disposal, 7) properly using formaldehyde solutions to treat contaminated areas when removal procedures are impractical (formaldehyde solutions are the only disinfectants proven to be effective for soil decontamination), 8) using water sprays or other dust suppressing techniques to reduce the amount of dust aerosolized during times of construction, excavation, or demolition in locations where H. capsulatum is endemic, This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 41 THE MENACING FUNGI 9) wearing National Institute for Occupational Safety and Health (NIOSH)-approved respirator and other equipment items by workers to reduce the risk of H. capsulatum exposure, using the appropriate respirator selected on the basis of the circumstances associated with airborne contaminant exposure in line with occupational exposure. Respirators provide different levels of protection. They are divided into classes based on assigned protection factors to provide comparisons of the protective capabilities in relation to other respirator classes. The protection factor assigned to a respirator is a unitless number determined statistically from a set of experimental or work place data. Regardless of which respirator is selected, the device should be NIOSH-certified, and used in the context of a respiratory protection program. (Additional information can be obtained from the following agencies: National Institute for Occupational Safety and Health, National Center for Infectious Diseases, the Centers for Disease Control and Prevention, or local health departments). THE IMMUNOCOMPROMISED PATIENT S ince 1987, disseminated histoplasmosis (DH) has been included among AIDS-defining infections. The disease state generally occurs when a patient’s CD4 + T lymphocyte count is <150 cells/mictoliter. The most frequently infected organs are the lungs and bloodforming organs, although all body organs are susceptible. Localized pulmonary histoplasmosis might occur among individuals with CD4+ T lymphocyte counts greater than 300 cells/ microliter. Without appropriate treatment, the disease has a rapidly fatal course. Individuals at Risk. In addition to persons with AIDS, other individuals are at risk for developing severe and disseminated histoplasmosis. These include persons with cancer, recipients of high-dose, long-term steroid therapy, and individuals undergoing cancer chemotherapy. PARACOCCIDIOIDOMYCOSIS P aracoccidioidomycosis (PCM) is an important systemic mycosis in Central and South America. The disease is frequently diagnosed in Brazil and Columbia. The lungs are the main target and the site at which both active and residual lesions appear regularly. Habitat Although the exact habitat of P. brasiliensis is not known, the pathogen occurs most often in subtropical forests. Isolations during the early history of the fungus were made from soil. The habit of cleaning teeth with twigs, grass and other pieces of vegetation may serve as the primary means of introducing the pathogen and initiating lesions in the oral mucosa, tongue, or gums. Culture and Microscopic Features Paracoccidioides brasiliensis is a large dimorphic fungus. In culture at room temperature, the fungus grows slowly and forms a white cottony mycelium consisting of very short hyphae This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 42 THE MENACING FUNGI without conidia. In tissues and laboratory cultures incubated at 370 C., the fungus takes the form of large spherical or oval cells capable of reaching diameters of 30 micrometers. Such distinctive large cells bear buds ranging in size from 1 to 5 micrometers in diameter. Transmission and Pathogenesis Humans probably acquire P. brasiliensis by the inhalation of conidia and mycelial fragments. These infectious particles reach the lungs, convert to the yeast form, and initiate the primary infection. The process usually is silent (asymptomatic), and may result in the appearance of signs and symptoms over the course of a few years. The silent course of the disease results in a steady progression of lung injury, which ultimately affects the health of patients. There is no evidence for person-to-person transmission. Clinical States The duration of PCM varies from a few months to 2 or 3 years. When the clinical manifestations become apparent, the disease may appear in several different forms. The most frequent site of primary lesions is the mouth, followed by the lungs, larynx, and skin, respectively. Table 8 list the known clinical forms of PCM together with their main clinical features. Table 8. The Clinical States Found with Paracoccidioidomycosis. Clinical Manifestation Feature(s) pulmonary lesions the lungs are the primary site and the main target of PCM; pulmonary involvement occurs in most individuals; the disease may appear as an acute-subacute (juvenile) form or chronic, adult form; the oral mucosa is usually the site of primary lesions; Signs and Symptoms: the lesions are bilateral and symmetrical with involvement of all pulmonary areas; cavity formation occurs with residual fibrotic lesions appearing in approximate 60 percent of patients; the progression of PCM results in the involvement of other body organs such as adrenal glands, liver, lymph nodes, spleen, and skin. oral lesions conspicuous lesions develop in the nasal or oral mucosa, the gums, and at times in the lining of the eyelid or the anorectal area; Signs and Symptoms: the oral infection can spread slowly producing severe, ulcerative and painful gum infection; This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 43 THE MENACING FUNGI gum lesions and those surrounding teeth loosen teeth which are lost by natural means or may require extraction; the loss of teeth, and gum involvement interfere with the feeding contributes to a rapid wasting of patients; these lesions may also appear on the plate, tonsils, and tongue. skin lesions a wide variety of skin lesions may occur; Signs and Symptoms: ulcerated, crusted lesions appear on the face resulting from an extension of lesions from the oral cavity or, are secondary to the spreading of PCM throughout the body via the circulatory system and result from lymph drainage. visceral lesions the lymphatic system, intestines, spleen and liver also are often infected in PCM; Signs and Symptoms: lesions typically develop in the spleen and the intestines; the stomach is rarely involved. Laboratory and Related Aspects of Diagnosis Laboratory diagnosis primarily depends on obtaining suitable specimens from lesions in the mouth and/or draining lymph nodes. Microscopic examination usually will reveal P. brasiliensis cells. Culture methods are also effective, but due to the slow growth rate of the pathogen, mycelia will not appear for at least 20 days. Radiologic abnormalities with this mycosis are often extensive and should alert physicians in areas where P. brasiliensis is endemic to the possibility of infection. In addition, individuals from endemic areas residing or visiting other parts of the world, and who have a history of chronic, nonspecific constitutional signs and symptoms should be examined radiologically. This type of inexpensive may reveal findings that are suggestive of PCM and provide an earlier opportunity to initiate treatment and to avoid or control the extensive fibrosis that occurs with the mycosis. Treatment Through the years has profoundly changed the outcome for patients with paracoccidioidomycosis. The most important advance was the introduction and use of the azole derivatives: ketoconazole and itraconazole. With these drugs, a relatively short course of treatment and few secondary effects usually is experienced by patients. A course of treatment with itraconazole with daily doses of 100-200 milligrams for 6 months has been found to be effective in approximately 95 per cent of patients with active disease. The relapse rate is around 5 per cent. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 44 THE MENACING FUNGI Despite the effectiveness of itraconazole treatment, the development of lung fibrosis does not appear to be modifies. Such fibrotic sequelae is related to the severity and infiltration of the pathogen and may be avoided to a large extent by prompt initiation of appropriate treatment. Prevention and Control The most obvious preventative measure in the prevention of PCM infection is the avoiding of contact with soil contaminated objects possibly containing conidia and/or mycelial fragments in endemic areas. THE OPPORTUNISTIC FUNGAL PATHOGENS THE ASPERGILLOSES A spergilloses are fungus diseases that occur worldwide and can affect all ages and sexes. These diseases can be broadly defined to collectively include any infection caused by a species of Aspergillus. One of the first identifiable cases of aspergillosis (singular form) was reported by the renown pathologist Rudolph Virchow in 1856. Several aspergilli are known to cause disease in lower animals as well. General Properties of the Aspergilli Aspergilli are rapidly growing molds producing fluffy, variously colored colonies (mycelia) within 2 days on laboratory media or food (Figure 15). Aspergillus species are identified on the basis of differences in their microscopic structures including hyphae (conidiophores) and the arrangement of spores (conidia). Figure 15. The appearance of mycelia. Two growths of two different aspergilli are shown. The greenish (lighter color) growth is that of A. flavus, and the black mycelium is that of A. niger. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 45 THE MENACING FUNGI Habitat The aspergilli are widely distributed in nature and found throughout the world. They are common inhabitants of soil, and air, and seem to adapt to a wide range of environmental conditions. Their natural ecological niche is the soil, wherein they survive and grow on organic matter. In general, because the majority of aspergilli live on decaying organic matter, they are considered to be saprophytes. Several species play essential roles in recycling environmental carbon and nitrogen. Since the aspergilli are capable of producing a large variety of digestive enzymes, they can use an enormous number of substances as nutrients, it is difficult to find a substance containing some organic matter and a little moisture on which these fungi cannot grow and reproduce. Microscopic and Cultural Properties In the clinical laboratory, aspergilli are easily isolated on most media used for fungi, and tend to reproduce in their asexual form (Figure 16). The microscopic appearance of these fungi in culture consists of long, branching filaments (hyphae) containing typical cross-walls. Hyphae may or may not give rise to asexual reproductive structures called conidiophores. The conidiophores arise directly from hyphae, and end in thick rounded heads known as vesicles. These vesicles may be either totally or partially covered by flask-shaped structures from which the reproductive units known as condiospores (conidia for short) are blown out into the surrounding environment. Every vesicle produces spores numbering in the thousands. While the size, shape, color, and thickness differ among the species of aspergilli, they generally have an average diameter of about 2.0 to 3 micrometers. Their small size allows for easy dispersion on air currents, and easy access to lung alveoli. Figure 16. A microscopic view of Aspergillus fumigatus showing hyphae, conidiophores (Cp), vesicles (V), and conidia (C). This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 46 THE MENACING FUNGI Aspergilli generally do not have elaborate mechanisms for releasing their conidia into the air. Spreading of the conidia relies on disturbances and strong air currents. Once in the air, the small size of conidia enables them to float, and to be airborne both indoors and outdoors. Interestingly, some environmental surveys indicate that all humans will inhale at least several hundred spores of Apergillus fumigatus conidia per day. A. fumigatus is the most common cause of Aspergillus infection worldwide. Aspergilli are rapidly growing molds producing fluffy, variously colored colonies known as mycelia (singular, mycelium) within 2 days on laboratory media or food stuffs (Figure 16). Aspergillus species are identified on the basis of differences in the structure of conidiophores and the arrangement of conidia. Nonpathogenic and Pathogenic Aspergilli Of the hundreds of recognized species of aspergilli, only a little over 20 have been verified to cause human infections, and only 5 of these consistently and regularly are encountered as causes of disease. Because of their great enzymatic capabilities, several aspergilli are used in various industrial processes. These include the commercial production of citric acid by A. niger for use by the soft drink industry, and the processing of soybeans by A. wentii in Japan. Aside from their disease causing-associations, certain aspergilli also cause considerable problems as contaminants in diagnostic laboratories by interfering with the isolation of various bacterial and fungus pathogens. Others reduce the commercial value of and ruin leather and cloth fabrics by being capable of growing on such products. The aspergilli impart a musty odor to clothes and shoes. In humid tropical climates, these are especially troublesome and individuals have to keep their wardrobes as dry as possible from being covered with heavy fungal growths. Mycotoxins. Aspergilli are often found growing on various types of foodstuffs, which they are capable of decomposing and causing decay. In so doing some species of Aspergillus and of other genera produce toxic substances known as mycotoxins. One of the most important of such poisonous products are the aflatoxins. These toxic metabolic products are associated with contaminated cereals, nuts, and animal feed. The aflatoxins as well as other mycotoxins are discussed in greater detail in a later section. Disease States. The most common Aspergillus species causing invasive disease include A. fumigatus, A. niger, A. terreus, and A. nidulans. Certain species are known to cause a variety of allergic states. These include A. fumigatus, and A. clavatus. Another important pathogen of the genus is the already mentioned A. flavus, which is known for the production of aflatoxins. The diseases caused by the aspergilli, and in particular A. fumigatus, can be divided into the following categories: 1. allergic reactions and complications caused by the presence of conidia or temporary This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 47 THE MENACING FUNGI growth of the fungi in the mouth, nose and other orifices; such allergic diseases include allergic sinusitis, alveolitis, and asthma will not be discussed in any great detail this course; 2. colonization without extension in preformed cavities and debilitated tissues within the respiratory tract, often called aspergilloma or fungus ball; 3. superficial infection of the skin paranasal sinuses (Figure 3), external ear canal, and more rarely, burn areas after sloughing of tissue, nails, and other body sites; 4. invasive, granulomatous, necrotizing infection of the lungs; and 5. systemic and fatal disseminated disease. The clinical aspects of several of these disease categories (to be described in a later section) are determined to a large degree by the general immunologic and physiologic state of the host. It should also be noted that certain forms of Aspergillus-caused diseases may become integrated or overlap within a patient Nosocomial Infections . Aspergillus species are infrequent causes of nosocomial infection. As a later section will discuss, pulmonary disease is the most common presentation. Wound infections occur much less frequently, but have been reported to occur after cardiac and abdominal surgery. Most surgery-associated infections appear to develop from the use of contaminated dressings, and airborne contamination of wounds in the operating theater. In 2003, hospital water systems and variable airflow volume (VAV) units located in air ducts just downstream from final filters in operating rooms were implicated as sources of nosocomial aspergillosis. The VAV units identified as sources of mold contamination were found to have insulation, which had deteriorated after becoming wet. Aspergillus conidia released from mold growing on the insulation were not effectively filtered out before entering the operating theater. Interestingly in this case, the source of the nosocomial outbreak was located by means of a closed-space video camera that allowed viewing of otherwise inaccessible ductworks. Nosocomial outbreaks are encountered most often during or after hospital construction or renovation, and usually in severely immunocompromised patients. ASPERGILLUS FUMIGATUS, AN IMPORTANT PATHOGEN I n the past 25 years, the mold Aspergillus fumigatus has gone from being a fungus commonly found in the environment and of minor interest, to one of the most important fungal pathogens. The main reason for this relatively sudden rise in status is the increase in systemic infections caused by this microorganism. A. fumigatus has become the most prevalent airborne fungal pathogen, causing severe and usually fatal invasive infections in immunocompromised hosts in developed countries. Although the conidia of A. fumigatus make up only about 0.3 percent of the fungal spores found in the air of a particular hospital, it causes roughly 90 percent of systemic Aspergillus infections. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 48 THE MENACING FUNGI Culture Features. A. fumigatus is known as a thermophilic species. It is capable of growing at temperatures as high as 55o C. and can survive temperatures up to 70o C. As most aspergilli, it is a rapid grower on laboratory nutrient preparations generally forming a gray-green pigmented mycelium (Figure 17). Figure 17. The characteristic gray-green pigmented A. funigatus mycelium. Pathogenicity To invade a host, A. fumigatus must be able to attach to and penetrate respiratory epithelial tissue and kill surrounding cells, specifically phagocytic cells, actively involved in protecting the body against invasion by A. fumigatus and other pathogens or opportunists. A. fumigatus has several virulence factors that contribute to its ability to cause disease or pathogenicity. These include the following: 1. spore size - the small size of A. fumigatus conidia (3 to 5 micrometers) permits penetration deep into the lung; in addition, such spores are capable of withstanding extraordinary conditions such as less than optimal host defenses; 2. spore pigment - the pigment of conidia provides some protection against phagocytosis by macrophages in the lungs and presumably in the nose; macrophage ingestion and killing of spores in the lungs is the first immunologic line of defense against Aspergillus; 3. adhesins - enable Aspergillus fumigatus conidia to bind specially to various circulating host proteins including fibrinogen, albumin immunoglobulins (antibodies), collagen, and complement; This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 49 THE MENACING FUNGI 4. enzymes - these proteins may provide protection against damage from hydrogen peroxide, singlet oxygen, hydroxyl, and other free radicals produced by phagocytes; they include superoxide dismutases, catalases, and phospholipases; these fungal enzymes can cause damage to host epithelial cells, protect against phagocytosis, and promote colonization of the lung; 5. toxic molecules - several metabolic products produced by the A. fumigatus are toxic to the host and can cause cell death, destruction of red blood cells, and suppress immune responses (immunosuppression); toxic products of A. fumigatus include hemolysin, a specific toxic molecule known as gliotoxin, and an enzyme to decompose ribonucleic acid.. Selected A. fumigatus-Associated Diseases For most individuals, respiratory tract is the main portal of entry and site of infection for A. fumigatus infections. Other sites have also been reported in immunocompromised patients and include the skin, bone, eyes, peritoneum, and the gastrointestinal tract. Allergic disease occurs following repeated exposure to conidia or Aspergillus-antigens in the absence of mycelial colonization of lung tissue, and in most cases, removal of the individual from the environmental source of the causative agent results in clinical improvement. In certain situations, a single parenchymal lesion may develop and subsequently heal with calcification to form a “coin lesion”. However, in clinically severe forms of aspergillosis, necrosis and pulmonary cavitation occur. Lesions in such situations continue to spread by radial extension of the mold’s hyphae beyond the cavity with eventual circulatory system spread to the kidneys and other body organs. Invasive Aspergillosis Invasive aspergillosis (IA) has long been recognized as a leading cause of death, mainly among hematology patients. The fungus infection, which follows solid-organ transplantation is most common in heart-lung transparent patients and is found, in decreasing order, in liver, heart, lung, and kidney recipients. Although IA is considered to be the main fungal infection in cancer patients, its true incidence is believed to be underestimated due to the low sensitivity of laboratory diagnostic tests. While IA is rarely found in immunocompetent individuals, it is reported to occur in AIDS patients, and is a common infectious complication of chronic granulomatous disease. Four types of IA are recognized. These are: 1. acute or chronic pulmonary aspergillosis (the most common form of the disease; This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 50 THE MENACING FUNGI 2. tracheobronchitis and obstructive bronchial disease with pseudomembrane formation and various degrees of invasion the mucosa and cartilage (this form seen predominantly in AIDS patients); 3. acute invasive rhinosinusitis; 4. disseminated disease (commonly involves the brain, skin, kidneys, heart, and eyes, and occurs in 10 to 40 percent of bone marrow transplantation (BMT) patients). Predisposing Factors. Patients at greatest risk for developing IA include: 1. recipients receiving bone marrow transplants from genetically unrelated individuals (allogenic BMT), who have a prolonged neutropenia or are under corticosteroid treatment for graft versus host (GVH) reaction or disease; 2. recipients of BMT from their own bone marrow (autologous BMT) or recipients of solid-organ transplants and who have been neutropenic for more than 2 weeks; 3. patients with acute leukemia and lymphomas undergoing intense chemotherapy; 4. patients with prolonged neutropenia and aplastic anemias that were not chemotherapeutically caused; 5. patients with previously documented aspergillosis and subjected to a new chemotherpeutic regimen or a BMT; 6. patients with neutrophil deficits as seen in cases of chronic granulomatous disease; 7. patients with advanced human immunodeficiency virus (HIV) disease. Gastrointestinal Involvement. Both inflammation of the mouth and invasive aspergillosis are common problems during radiation therapy and cytotoxic chemotherapy for hematological malignancies such as acute leukemia. Certain studies have demonstrated that the gastrointestinal (GI) tract (including the oral cavity) can be a common target for invasive aspergillosis. It remains unknown whether invasive gastrointestinal aspergillosis is primary or secondary in origin. Aspergillus species may invade through the GI tract after disruption of the intestinal mucosal barrier caused by chemotherapy, or they may spread from the lungs by means of the circulatory system. Early diagnosis of GI aspergillosis and prompt initiation of appropriate therapy pose problems if invasive gastrointestinal aspergillosis is not considered as a possible complication of patients undergoing cytotoxic therapy for hematological malignancies. Liver Transplant Recipients. IA has been a long time, major problem in liver transplant recipients. Virtually all liver transplant patients with IA have evidence of significant hepatic and/or renal dysfunction. Studies also have shown that recipients of a liver retransplantation This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 51 THE MENACING FUNGI have a risk for IA that is 30-fold higher than that of other patients. A study reported by N. Singh and associates in 2003, demonstrated that the risk profile and the epidemiology of IA in liver transplant recipients has changed. The disease seen in the current era occurs later, is less likely to be associated with central nervous system infection, and has a lower mortality rate when compared with IA seen in the early 1990’s. Signs and Symptoms. Clinical signs and symptoms are usually too nonspecific to be helpful in diagnosing IA. As with other forms of aspergillosis, patients primarily experience chest pain, cough, fever, general discomfort, difficulty in breathing, and weight loss. A positive CT scan may be the first definitive suggestion of IA. Diagnosis. The diagnosis of IA generally involves at least lines of evidence of infection. These are: a positive computerized axial tomogram (CAT scan), a positive culture and/or microscopic demonstration of Aspergillus fumigatus, and detection of Aspergillus antigens in a patient’s serum. In early stages of IA, CT scans may reveal specific signs of infection such as the typical “halo” resulting from hemorrhagic necrosis surrounding a fungal lesion or pleura-based lesions. CT scanning can be used in conjunction with brain magnetic resonance imaging with cerebral aspergillosis patients. Other Aspergilloses Caused by A. fumigatus Table 9 summarizes other examples the most common clinical manifestations caused by A. fumigatus. Note that in this table, the approaches to diagnosis are provided in the form of footnotes for the respective manifestations since these conditions are quite specific. Table 9. Aspergillus fumigatus Clinical Manifestations Clinical Manifestation Distinguishing Features allergic bronchopulmonary (ABPA) most severe allergic pulmonary complication aspergillosis caused by Aspergillus species; occurs in patients with chronic lung disease, especially asthma, chronic obstructive pulmonary disease, or cystic fibrosis; follows the same course as classic asthma, with a unique cellular immune response and pathophysiologic findings caused by responses to products of T-lymphocytes; effects range from asthma to lethal destruction of the lungs. Signs and Symptoms: manifests itself as a bronchial asthma with temporary pulmonary infiltrates that may proceed to proximal bronchiectasis and lung fibrosis; central bronchiectasis generally is detected in the late This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 52 THE MENACING FUNGI stages of the disease; patients exhibit remittent low-grade fever, weight loss, difficulty in breathing, coughing, and the production of a foul smelling sputum in the morning or when changing position. In untreated patients, ABPA eventually progresses to pulmonary fibrosis and respiratory failure. ABPA presents diagnostic difficulties, which have led to the concept of “silent” ABPA. Some cystic fibrosis patients in whom the classic diagnostic criteria have not been met, for example, experience damage to their respiratory mucosa in response to exposure to Aspergillus conidia. a aspergilloma in the early 1950’s, aspergilloma was the classical form of aspergillosis; occurs in preexisting pulmonary cavities caused by tuberculosis, sarcoidosis, conditions characterized by deep-seated vesicles, and chronically blocked paranasal sinuses. aspergilloma, also referred to as “fungus ball,” consists of a sphere-shaped mass of fungal hyphae embedded in a proteinaceous substance with conidia-forming structures at its edges; aspergillomas are found external to the cavity lining; on chest radiographs an aspergilloma appears as a spherical mass surrounded by a radiolucent crescent. Signs and Symptoms: patients are usually asymptomatic; marked pleural thickening typically occurs; a common sign of aspergilloma is the spitting of blood coming from the bronchi or lungs (such hemoptysis results from the disruption of blood vessels in the wall of the cavity occupied by aspergilli, or in the bronchial artery supply centimeters away from the aspergilloma). b a ABPA is a difficult condition to diagnose. The classic criteria listed for a definitive diagnosis include asthma, a history of pulmonary infiltrates, central bronchiectasis, immediate skin reaction within 10 to 20 minutes following the application of A. fumigatus antigenic extracts. b Aspergillomas are most often found on chest radiographs obtained for the evaluation of another pulmonary or allergic disease. Computed tomography (CT) scans of the chest are of great value in diagnosis. In addition, a significant increase in anti-Aspergillus fumigatus antibody occurs as patients recover. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 53 THE MENACING FUNGI Laboratory diagnosis includes the isolation of A. fumigatus and the finding of large numbers of eosinophils in the peripheral blood and Charcot-Leyden crystals in brown plugs from sputum specimens and related secretions. Elevated levels of immunoglobulin E (IgE) to A. fumigatus in serum and immediate skin reactivity (within 15 +/- minutes) after the application of A. fumigatus antigenic extracts also are important to the diagnosis of the disease Major Syndromes Found with AIDS Patients Two major Aspergillus species-syndromes can be found with patients with AIDS. These are respiratory tract disease (either semi-invasive pseudomembranous tracheitis or invasive pneumonitis) and central nervous system (CNS) infection presenting as a febrile diffuse meningoencephalitis. Vascular infarction is a central feature of the CNS infection. The signs and symptoms of the respiratory tract disease states are given in Table 10. Table 10. Major Syndromes Found with AIDS Patients Syndrome semi-invasive pseudomembranous tracheitis invasive pneumonitis Signs and Symptoms cough, dyspnea, fever, stridor or wheezing caused by airway constriction culminating in airway obstruction if untreated; endoscopic examination show a confluent, exudative pseudomembrane sticking to the tracheal wall chest pain, cough, fever, hemoptysis, and hypoxemia; radiographs show either a diffuse interstitial pneumonitis or a localized wedge-shaped dense infiltrate representing a pulmonary infarction. General Aspects of Laboratory Diagnosis Establishing a laboratory diagnosis of invasive infection due to Aspergillus species can pose difficulties. Convincing evidence includes the isolation and growth of Aspergillus species from specimens obtained from normal sterile sites or histopathological findings showing the presence of fungal elements invading tissue. Such elements would include typical branching hyphae and spores (Figure 18). Specimens of value for the isolation of aspergilli include bronchoalveolar lavage fluid (BAL), sputum, and nasal swabs. Bronchoscopy may also provide a suitable specimen for culture. The specimens-of-choice are BAL samples, percutaneous lung biopsy, or aspirated specimens obtained with radiological or ultrasound guidance. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 54 THE MENACING FUNGI Figure 18. The microscopic features of a histopathologic examination of tissue taken from an individual with invasive aspergillosis. The branching hyphae and spores typical of aspergilli are shown in this stained preparation. Pathogenic aspergilli generally grow easily and relatively rapidly on routine media preparations used for fungal isolations. Typical mycelia only pathogens are capable of growing at 35 to 37 o C. In addition, A. fumigatus has the unique property of being able to grow and reproduce at temperatures of 50o C or higher. Serological testing for the detection of circulating Aspergillus antigens or antibodies can be very helpful in the diagnosis of aspergilloma or ABPA, the aspergilloses observed in immunocompetent individuals. Of the more than 20 diagnostic procedures, the techniques that appear to be the most reliable to detect anti-Aspergillus antibodies are double immunodiffusion and counterimmunoelectrophoresis. Radioimmunoassays and enzyme-linked immunosorbent assays (ELISAs) are used for the detection of circulating Aspergillus antigens. In the case of immunosuppressed individuals, an increase in the concentration (titer) of antiAspergillus antibody at the end of immunosuppression indicates recovery from IA, whereas an absence of antibody or declining antibody titers is suggestive of a poor prognosis. The detection of circulating antibodies to Aspergillus, thus has prognostic and not diagnostic value in immunosuppressed patients. The serological diagnosis of IA is based on the detection of circulating Aspergillus antigens, not anti-Aspergillus antibodies, in biological fluids such as serum, urine and BAL specimens. Treatment Until recently, there were only two antimycotic agents with activity against Aspergillus species, This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 55 THE MENACING FUNGI amphotericin B deoxycholate (AmB-d) and itraconazole. Despite advances in newer antifungal agents, AmB-d remains the treatment of choice for invasive aspergillosis. The effective use of this antimycotic may be complicated or limited by potential adverse effects such as renal impairment. The therapeutic options available to treat IA are limited to a small number of antifungal compounds. Since approximately the early 1980’s, deoxycholate amphotericin B has been used as the standard antifungal agent for the treatment of IA in severely immunocompromised patients. This has been largely because of the drug’s long historical record and the absence of suitable parenteral antifungal alternatives. The usefulness of amphotericn B, depending on the patient involved, can range from 10 to 40 percent largely because its toxicity. Newer antifungal agents such as the triazoles, itraconazole and voriconazole, are used for IA treatment. However, the effectiveness of these agents may be hampered by drug-related liver toxicity and hazardous drug interactions in patients. More recently, the use of caspfungin, an echinocandin, has been found to be well tolerated by IA patients who were refractory to standard therapy. In addition, the antifungal agent’s-toxicity level was minimal. Prevention and Control Rapid diagnosis and appropriate therapy are essential to the prevention and control of the various forms of aspergilloses. Quarantine measures are not indicated. In addition, there are no vaccines. In cases of allergic diseases, such as asthma, allergic sinusitis, and alveolitis approaches to prevention include, ordinary cleaning procedures directed at removal of fungal conidia, and if possible, removing the allergic individual from the environmental sources of the fungi. In health care facilities, the use of high efficiency particulate air (HEPA) filters, are effective in removing conidia and related fungal components. Inspection of filter systems on a regular basis and replacement of defective filters is essential to preventing and decreasing the incidence of invasive aspergillosis and other of the aspergilloses in immunosuppressed patients. Ordinary cleaning procedures also are important in prevention and control. CANDIDIASIS AND CANDIDA SPECIES C andidiasis is an acute or chronic, superficial or disseminated mycosis, caused by various Candida species. C. albicans is the most common species associated with disease. The clinical manifestations of this group of fungal pathogens are extremely are extremely diverse. In recent years Candida species have come to be recognized as the most common cause of fungal infections among HIV-infected children. Pathogenic Candida Species Several Candida species have been identified on the basis of a combination of biochemical and This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 56 THE MENACING FUNGI structural properties. The species commonly associated with human disease include the following: 1. C. albicans 2. C. dubliniensis 3. C. glabrata 4. C. guilliermondii 5. C. krusei 6. C. parapsilosis 7. C. tropicalis Habitat Candida albicans is a common member of the microbial populations in different sites of the human body. The human is the reservoir of the yeast. C. albicans occurs worldwide and is usually normally found in small numbers on the mucous membranes of the oral cavity, lower intestinal tract, and female genital tract. This colonization is aided by the ability of the yeast o attach to mucosal cells, a property that distinguishes it from other Candida species. Changes in host immunity such as significant reduction in or depletion of the CD4+ lymphocytes in patients with AIDS result in disease at these sites. Invasive disease can occur as a result of neutropenia after cancer immunotherapy or in individuals who have undergone a transplantation procedure. Transmission Most C. albicans infections are caused by the yeast normally found in the body’s microbial (endogenous) population. This is the case with most nosocomial infections as well. Infections also can occur as a result of direct contact with lesions in other individuals such as through unprotected sexual intercourse, and in situations involving invasive surgical procedures. Neonatal infections may also result from passage through an infected birth canal, or exposure to infectious vaginal secretions shortly after birth. Risk Factors . In order for Candida species to act as pathogens, interruption of normal host defenses is necessary. General risk factors for Candida infections include diabetes mellitus, immunocompromised states including HIV-infection, immunosuppression, and iatrogenic factors such as antibiotic use, indwelling devices (pacemakers, and urinary or vascular catheters), surgery, intravenous drug use, and hyperalimentation fluids. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 57 THE MENACING FUNGI Medical Devices and Biofilms . The combination of an increasing aging population and consistently growing number of inserted medically-related devices is quite likely to escalate the occurrence of infectious complications related to medical devices. At least half of all cases of nosocomial infections are associated with such devices. The medical consequences of devicerelated infections can be disastrous, and include potentially life-threatening systemic infections and device malfunction that may require its removal. The removal of medical devices is often complicated by tissue destruction. An increasing proportion of device-related infections, particularly those involving the bloodstream and urinary tract, are caused by Candida species. A significant proportion of human infections involve microbial biofilms. Such biofilms develop when microorganisms adhere (stick) to a surface and produce extracellular multiple units (polymers) of carbohydrates, or proteins, that provide a matrix (basic structural surrounding substance) and aid in further attachments. Microorganisms in biofilms behave differently from freely suspended microbes and have been shown to be relatively refractory to medical therapy. Both bacteria and Candida species within biofilms are markedly resistant to antimicrobial agents Thus, biofilm associated infections of retained medical devices may recur after cessation of antibiotic therapy and may require device removal. Candida species are emerging as important nosocomial pathogens, and an implanted device with a detectable Candida-biofilm is frequently associated with infection. Candida albicans biofilm formation has the following 3 developmental phases: 1. early phase - yeast cell adheres to device surface, 2. intermediate phase - matrix formation with yeast cells changing to hyphal forms, 3. maturation phase - substantial increase in matrix material. Fully formed (mature) Candida biofilms contain a mixture of yeast cell, hyphae, and pseudohyphae in a matrix consisting of carbohydrate, protein, and unknown components. The formation of such biofilms is influenced by the chemical make-up of the contact surface, environmental factors, the development of Candida phases, and the Candida species involved. Culture and Microscopic Properties Candida albicans grows in either of two basic forms, yeast and hyphal. The yeast form with buds is seen under most conditions (Figure 19.) The hyphal forms begin with what appears to be elongated blastospores extending out many times the diameter of the original cell. Such situations may result in the formation of several cells being connected into what is called pseudohyphae. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 58 THE MENACING FUNGI Figure 19. A scanning micrograph showing the yeast form with smaller buds connected to several of them. Most Candida species grow rapidly on enriched laboratory media and appear a smooth, white to cream colored colonies measuring 2 to 4 millimeters in diameter. These growths resemble bacterial colonies rather than the typical mold mycelia. On special media C. albicans forms sproutlike distinctive hyphae know as germ tubes. This yeast also forms thick-walled spores called chlamydoconidia, which distinguishes it from other Candida species. Figure 20 shows a microscopic view of characteristic C. albicans chlamydospores and clusters of blastospores. Figure 20. A microscopic view of the large spherical C. albicans chlamydospores and the smaller blastospores appearing in clusters. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 59 THE MENACING FUNGI Disease States As indicated earlier, Candida infections are quite numerous and variable. Table 11 lists the most commonly encountered forms together with their clinical signs and symptoms. Table 11. Candida Clinical Manifestations Clinical Manifestation Distinguishing Features bronchocandidiasis chronic bronchitis. Signs and Symptoms: cough, varying amounts of sputum, medium and coarse rales at the lung bases; roentgenologic appearance of peribronchial thickening, hazy linear fibrosis. candidids represents local skin reaction to circulating Candida antigens. Signs and Symptoms: red area with little blisters; usually appear in areas distant from infected skin sites; itching is quite common. endocarditis condition resembles bacterial endocarditis; it differs mainly in the greater presence of large vegetations (growths) on heart valves, and emboli associated with major blood vessels such as the splenic, renal, and iliac arteries. Signs and Symptoms: anemia; congestive heart failure, fever, heart murmur, and enlarged spleen. esophageal candidiasis typical signs and symptoms may be absent; found with low CD4 + counts; Signs and Symptoms: inability or difficulty to swallow; pain on swallowing; retrosternal pain; dehydration; weight loss (especially in children); the presence of oropharyngeal candidiasis may or may not be present; Children, unlike adults might experience nausea and vomiting. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 60 THE MENACING FUNGI fungemia (septicemia) mainly results as a rapidly fatal conclusion to some underlying condition such as immunosuppression, and malignancies. Signs and Symptoms: fever impaired renal function, leukopenia. generalized cutaneous candidiasis condition seen most often in individuals with diabetes, some form of immunosuppression such as HIV-infection or AIDS, or with congenital skin defects, and during pregnancy. Predisposing Factors : diabetes, obesity, alcoholism, immunosuppression, and continual and routine immersion of hands in water or other irritating substances associated with certain occupations. Signs and Symptoms: skin lesions are red, scaling, moist or weeping and exhibit sharp borders and may occur in body areas such as the armpits, groin, gluteal folds, mouth, nails, perineum, and between fingers; central areas of such lesions may have blisters, and pus-containing centers; This clinical manifestation usually is associated with oral lesions, infections involving various structures of the mouth, and heavy intestinal colonization resulting in gastrointestinal discomfort. intertriginous candidiasis this condition is quite similar in most respects to the features listed for generalized cutaneous candidiasis condition seen most often in individuals with diabetes, some form of immunosuppression such as HIV-infection or AIDS, or with congenital skin defects, and during pregnancy. Predisposing Factors : diabetes, obesity, alcoholism, immunosuppression, and continual and routine immersion of hands in water or other irritating substances associated with certain occupations. Signs and Symptoms: skin lesions are red, scaling, moist or weeping, painful, itching, and exhibit sharp borders and may occur in body areas containing skin folds (intertriginous) such as the armpits, groin, gluteal folds, mouth, nails, perineum, and between fingers, central areas of such lesions may have blisters, and pus-containing This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 61 THE MENACING FUNGI of such lesions may have blisters, and pus-containing centers; meningitis serious condition that may result in significant morbidity and mortality if not detected and treated effectively; Predisposing factors: previous antibiotic or corticosteroid therapy, malignant disease, immunosuppressed states; in adults postoperative complications of neurosurgery, result of disseminated disease, or immunosuppession. Signs and Symptoms: contracted pupils, convulsions, delirium, fever, intense headache, lethargy, loss of appetite, nausea and vomiting, sensitivity to light and/or sound, onychia and paronychia a localized form of Candida infection involving the nails and/or nail bed; condition is an inflammation of the subcutaneous tissues at the base of finger or toenails (onychia), or the marginal structures around the nail (paronychia). Predisposing factors : malignant disease, immunosuppressed states, or occupational exposure to excessive moisture and/or chemicals causing injury to nails; in adults postoperative complications of neurosurgery, result of disseminated disease, or immunosuppession. Signs and Symptoms: prominent swelling redness, and pain extending as far back as 1 centimeter from the edge of the nail; very little pus formation unless there is a mixed infection with bacteria; nails may become brown, exhibit lines, or brittle. oral candidiasis (thrush) condition seen most often in individuals with a riboflavin deficiency, diabetes, some form of immunosuppression such as HIV-infection or AIDS, and during pregnancy; condition is also seen among infants and results from passage through an infected birth canal; occasional epidemic of oral thrush can also occur in nurseries; the elderly also experience oral thrush largely because of the presence of a debilitating disease. Signs and Symptoms: discrete or confluent patches of a cream-white to gray pseudomembrane cover various parts of the oral cavity including the tongue, soft palate, and This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 62 THE MENACING FUNGI of the oral cavity including the tongue, soft palate, and gums; removal of patches may cause bleeding; membrane may extend and penetrate deeply into tissues to be painful and to interfere with swallowing; in severe cases with infants interference with breathing may occur; enlargement of projections of the tongue (papillae) can result in a condition known as “black hairy tongue”; Oral candidiasis often extends to the corners of the mouth which results in painful, bleeding slits or deep lesions. oropharyngeal esophagitis very common among HIV-infected children; Signs and Symptoms: the presence of a creamy white curd-like (cottage cheese consistency) patches with inflamed underlying mucosal on the palate, tonsils, and oropharyngeal mucosa; raised white plaques on the lower tongue surface, palate, and mucosal surfaces; red crack-like sores in the corner of the mouth. pulmonary candidiasis Candida albicans and other species can cause disease at various levels of the respiratory tract, can easily colonize mucosal surfaces damaged by other microbial pathogens. Signs and Symptoms: cough with mucoid and sometimes blood-streaked sputum, effusion, low grade fever, medium moist rales, pleurisy; altered breath sound develop with severe confluent lesions, bronchopneumonic lesions may extend yo result in lobar pneumonia. vulvovaginal candidiasis (vaginal thrush) condition seen most often in women with diabetes, some form of immunosuppression such as HIV-infection or AIDS, and during pregnancy. Signs and Symptoms: vaginal itching, burning sensation on urination, presence of a cottage cheese-like discharge, abscesses and kidney involvement may also occur in untreated cases. Individuals At Risk Candidiasis occurs in a variety of conditions including persons with AIDS, patients in an ICU after general surgery, patients immunosuppressed resulting from chemotherapy and related procedures, and in patients with liver diseases. Factors such as the administration of supraphysiologic doses of adrenal corticosteroids, the use of indwelling intravenous catheters, This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 63 THE MENACING FUNGI and low birth weight in neonates are known to predispose individuals to deep candidiasis. Of particular concern is candidiasis occurring among HIV-infected children. It is the most common fungal infection found this group of individuals. Oral thrush and diaper dermatitis ranges from 50 to 85 percent among HIV-infected children. In the United States, Candida albicans-caused esophagitis is reported as the AIDS-defining condition in adults and in about 12 to 16 percent of children less than 13 years of age. This condition continues to be seen in the post-HAART (highly active antiretroviral therapy) era among children not responding to therapy. While disseminated candidiasis (candidemia) is infrequent among HIV-infected children, Candida species can spread from the esophagus particularly when coinfections with herpes simplex virus or cytomegalovirus are present. Infection can also develop from chronically indwelling central venous catheters used for total parental nutrition or intravenous antibiotics. Approximately 50 percent of reported cases are caused by non-C. albicans species including C. dubliniensis, C. glabrata, C. krusei, C. parapsilosis, C. pseudotropicalis, and C. tropicalis. Treatment Eliminating possible underlying causes of candidiasis such as the removal of indwelling venous catheters, and diabetes control often facilitates cure. C. albicans is usually susceptible to amphotericin B, nystatin, flucytosine, and an azole such as clotrimazole, fluconazole, or ketoconazole. Table 12 lists several examples of the drugs used to treat various form of candidiasis. Table 12. Examples of Drugs Used to Treat Candidiasis Infection or Disease State Treatment oral and esophageal candidiasis fluconazole oral thrush nystatin suspension, itraconazole suspension, fluconazole vaginal thrush oral fluconazole, or topical butoconazole, clotrimazole, micoazole, nystatin,terconazole visceral/invasive candidiasis amphotericin B with or without 5-flurocytosine Diagnosis Diagnosis of candidiasis requires evaluation of both clinical and laboratory findings. The most valuable laboratory evidence of infection is the microscopic demonstration of Candida yeast cells and/or pseudohyphae in infected tissue or body fluid specimens. Specimens usually are suspended in potassium hydroxide to reveal the yeast cells. Laboratory confirmation with positive cultures finding also is important. A direct aspirate, biopsy, or bronchoalveolar lavage This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 64 THE MENACING FUNGI (BAL) is often required to establish diagnosis of deep organ involvement. The finding in severe or recurrent oropharyngeal infection in an adult patient with no obvious underlying cause should suggest the possibility of HIV infection. The presence of systemic Candida infection requires the culturing of blood specimens. In such cases several other diagnostic approaches might be appropriate. The include the following: 1. retinal examination for endophthalmitis, 2. abdominal computerized tomography or ultrasound for hepatic or renal involvement, 3. bone scans for osteomyelitis. Prevention and Control Early detection and appropriate treatment of any infection involving the oral cavity, esophagus, or urinary bladder, especially in persons with the risk factors indicated earlier is extremely important to prevent possible systemic spread of candidiasis. In addition, secretions and contaminated articles should be disinfected. In cases of vaginal infection, additional steps can be taken. These include avoiding the wearing of tight undergarments and jeans, and the use of deodorant tampons and feminine hygiene products if the signs and symptoms of an infection are apparent. Since Candida grows and reproduces well in warm, moist environments, the genital area should be kept dry. CRYPTOCOCCOSIS C ryptococcus neoformans is the infectious causative yeast of the disease known as cryptococcosis. Formerly a rare disease, the incidence of cryptococcosis has increased in recent years because of its frequent occurrence in persons with AIDS. Cryptococcosis is the fourth most common opportunistic infection in AIDS patients after Pneumocystis carinii pneumonia, and cytomegalovirus and Mycobacterium avium complex infections. This yeast infection is classified as an AIDS-indicator opportunistic disease. Two varieties of C. neoformans are recognized. These are C. neoformans variety (var.) neoformans and C. neoformans var. gattii. The two varieties exhibit a difference in geographical distribution with C. neoformans var. neoformans being found worldwide, and C. neoformans occurs mainly in tropical and temperate climates. Attention will be limited to C. neoformans var. neoformans since infections caused by this yeast are far more frequent. Habitat C. neoformans (cryptococcus) is found in soil contaminated with pigeon or the droppings of other birds such as sparrows and starlings. The yeast also has been recovered from the dried excreta of chickens, the beaks and feet of pigeons, and from bat droppings. Cryptococcus does This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 65 THE MENACING FUNGI not cause disease in pigeons or other bird species, presumably because the body temperature of these animals is too high for the growth and reproduction of the yeast. Bats also can be infected with C. neoformans. This yeast gains a competitive advantage over other microbes by being able to grow and multiply exceedingly well in a dried bird droppings accumulated in places that are not in direct sunlight. Microscopic and Culture Properties Cryptococcus neoformans is a spherical yeast which reproduces by budding at any point on the surface. Sometimes several buds are formed simultaneously (Figure 21). Figure 21. A microscopic view of Cryptococcus neoformans and its buds suspended in an India ink preparation. Individual cells measure approximately 4 to 6 micrometers in diameter and characteristically can form an outer structure known as a capsule (Figure 22). The capsule, which is unique among pathogenic fungi, contributes to the disease producing capability of the pathogen by interfering with host immune processes such as phagocytosis. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 66 THE MENACING FUNGI Figure 22. A microscopic view of an India ink preparation of Cryptococcus with a bud and surrounded by an outer capsule. The capsule appears as a halo surrounding this yeast and its bud. Transmission The mode of transmission for C. neoformans is through inhalation of the pathogen. Cryptococcosis is not contagious. Pathogenesis Cryptococcal infection is believed to start with the inhalation of C. neoformans from an environmental source, followed by pulmonary infection or disease. In most individuals the signs and symptoms are minimal. Occasionally the infectious process progresses in the lungs and is spread via the circulatory system to the central nervous system and other areas of the body. Initial interactions with immune system cells such as alveolar macrophages are crucial in the outcome of cryptococcal infections. Nonencapsulated C. neoformans are generally engulfed and destroyed by polymorphonuclear leukocytes. However, encapsulated forms of the pathogen (Figure 21) are capable of escaping from the clutches of such host cells. Specific antibody enhances phagocytosis and the killing of the cryptococci. The polysaccharide capsule of cryptococci also can interfere with other host immune mechanisms. The circumstances are identical to those occurring with encapsulated pneumococcus. Tissue reactions to the pathogen vary from none to pus formation and tumor formation. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 67 THE MENACING FUNGI Risk Factors Before 1946, only 200 or so cases of cryptococcosis had been reported in the medical literature. By 1955, many more cases had been reported and repeated isolation from environmental sources also had been described. Cryptococcosis generally remains localized in immunocompetent individuals and resolves. The disease is relatively rare among immunocompetent person. However, the infection is one of the most frequent fungal infections occurring in persons with AIDS. In such cases, the pathogen is known to readily spread from the lungs to the central nervous system. Individual experiencing other conditions that impair their immunity also are susceptible to C. neoformans infection. Examples of such conditions include alcoholism, chronic corticosteroid therapy, Cushing’s syndrome, malignancies of various types, neutropenia after cancer immunotherapy, sarcoidosis, and tissue transplantation procedures. Clinical States In most situations cryptococcus infection begins as a pulmonary disease with hematogenous spread to the skin, bones, abdominal viscera, and especially to the central nervous system. A temporary pulmonary lesion does develop which either heals by the body enclosing it in a sheath or capsule (encapsulation) leaving a cryptococcoma, or heals without leaving any residual scar. Table 13 lists the most commonly encountered forms of cryptococcal clinical infections together with their signs and symptoms. Table 13. Cryptococcus Clinical Manifestations Clinical Manifestation Distinguishing Features benign pulmonary cryptococcosis represents mild or minimal exposure; may be manifested only an accidental autopsy finding of an encapsulated, healed subpleural tumor; with active lesions, masses of pathogen penetrate the bronchus wall, displace host tissue, and large numbers of Cryptococcus are discharged into sputum; pulmonary lesions do not calcify upon healing, and most heal without leaving residual evidence of infection. Signs and Symptoms: cough, scanty mucoid or bloodtinged sputum; low grade fever, malaise, and weight loss may occur in some cases; bronchitis, consolidation, dullness to percussion, rales or pleural effusion may also be present. cutaneous cryptococcosis may be a site or sites of primary inoculation with pathogen; may accompany a systemic infection and probably is preceded by a respiratory infection; This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 68 THE MENACING FUNGI Signs and Symptoms: lesions may take the form of papules (small, elevated, hard red areas on the skin) pusfilled blisters, or subcutaneous abscesses which form ulcers. Mucosal lesions may also develop as a result of hematogenous spread or by extension of skin lesions; may be in the form of small lumps, or superficial ulcers on any oral or nasal mucosal surfaces. meningitis most commonly recognized form of cryptococcal disease; the usual course is fairly rapid and marked by progressive deterioration of the individual; the infection is more rapid in AIDS patients. Signs and Symptoms: insidious onset with relatively nonspecific finding until late in the course of the infection; dizziness; intermittent headache; irritability; difficulty in performing complex cerebral functions gradually appear over weeks or months with no consistent pattern; fever usually present. Later in clinical course of the disease: seizures, cranial nerve signs, edema and inflammation of the optic nerve, dementia, and decreased levels of consciousness. osseous cryptococcosis occurs in about 10 percent of reported cases of crytococcosis lesions spread slowly, destructive to bone spread to the skin by extension or tissue, and often following some type of surgical exploration. Signs and Symptoms: frequently associated with bone pain and swelling occur for several months. visceral cryptococcosis may resemble tuberculosis; lesions also are suggestive of a malignancy. Signs and Symptoms: swelling and inflammation of the optic nerve; inflammation also involving the retina, and cornea. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 69 THE MENACING FUNGI Treatment Amphotericin B either alone or in combination with 5-fluorocytosine is effective in many situations of systemic disease. Cryptococcus infections present problems in AIDS patients. In such cases fluconazole is beneficial after an initial course of Amphotericin B and is continued indefinitely. Unfortunately, one-half of cured individual experience some type of neurologic damage Diagnosis In all cases of diagnosis, it is important to note that the number of cryptococci is quite small. Demonstrating the pathogen in clinical specimens such as spinal fluid, is diagnostic. The use of India ink for material microscopically examined is standard (Figures 20 and 21). Culture also is effective. However, a large amount of specimen is usually necessary. Other approaches to diagnosis include detection of capsular material by procedures such as enzyme immunoassays. Prevention and Control The chemical disinfection of accumulated pigeon droppings followed by their appropriate removal and disposal is recommended as a preventative and control measure. The droppings should be adequately wetted by a chemical agent such as iodophor to prevent aerosolization of any pathogens present. Any body fluids, surgical dressings and/or other types contaminated articles should be disinfected as well. PENICILLIOSIS P enicilliosis is a systemic and progressive infection caused by Penicillium marneffei. Infections with this pathogenic fungus are becoming increasing common in Southeast Asia, and is now recognized as one of the most frequently encountered opportunistic infections among person with AIDS. However, cases of infection have also been reported in immunocompetent individuals. Geographic Distribution and Habitat The first natural case of human penicilliosis was reported in 1973, in a 61-year old male U.S. citizen who had traveled to Southeast Asia. This person had Hodgkin’s disease, and was diagnosed with P. marneffei infection on being found to have a splenic abscess. A second case was found approximately 10 years later in a U.S. male who had traveled throughout Southeast Asia. Between 1988 and 1994, 14 AIDS-associated penicilliosis cases were reported among HIV-infected persons returning to their respective native countries after visits to Southeast Asia. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 70 THE MENACING FUNGI From the gathered epidemiological data, P. marneffei infections are most common in northern Thailand, and the southern part of the People’s Republic of China (Guang Xi Province). The pathogen in all probably resides in soil where it reproduces. Culture and Microscopic Features P. marneffi is a dimorphic fungus. When grown on appropriate laboratory media at room temperature the mold produces a distinctive red pigment, which diffuses into the medium. Transmission Humans acquire penicilliosis by inhaling the spores of the mold. Clinical States The incubation period of disseminated P. marneffei infection is variable. In some cases symptomatic disease appears within a few weeks after exposure. In others, victims are reported to have long periods without any signs or symptoms. Signs and Symptoms. The most common clinical features include anemia, fever, lymphadenopathy, enlarged liver and spleen, nonproductive cough, and marked weight loss. About 60 to 70 percent of patients exhibit a large number of papular skin lesions (solid, red elevated areas), which may become centrally necrotic. Chest radiographs may show infiltrates or cavitary lesions. Treatment Amphotericin B is the drug-of-choice for severe cases. The usual dosage administered is 1 milligram (mg)/kilogram of body weight daily for 2 weeks, after which itraconzaole (200 to 400 mg daily) or ketoconazole (400 mg) should be given for 6 weeks. An azole drug can be used for treatment of milder infections. Fluconazole, while being less effective than itraconazole, can be useful with patients who fail to absorb itraconazole. Laboratory and Related Aspects of Diagnosis Diagnosis can be made by direct microscopic examination of stained clinical specimens such as, skin, bone marrow, lymph nodes, and other infected sites, or culture material. The pathogen typically exhibits round or oval cells with prominent cross walls. The culture of specimens is critical to diagnosis since other system infections such as cryptococcosis and histoplasmosis have similar clinical manifestations. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 71 THE MENACING FUNGI Prevention and Control Avoiding environmental sources of P. marneffi is difficult. The highest number of cases appear to occur during the rainy season from May to October. Immunocompromised individuals should be advised about the risk of acquiring penicillinosis when traveling to areas of Southeast Asia and the southern part of the People’s Republic of China, where P. marneffei is known to be endemic. THE MYCOTOXICOSES The Major Mycotoxins F ungal pathogens, in addition to causing infection, can also have an impact on human health by producing harmful toxins, and/or initiating allergies. Table 14 lists representatives of known major mycotoxins (fungal poisons) and their modes of action. Table 14. Representative Known Major Mycotoxins and Their Actions Mycotoxin Main Fungus Source(s) Examples of Food Sources aflatoxins a Aspergillus flavus and A. parasiticus and other Aspergillus species contaminated cereals, figs, oil seeds, nuts, tobacco, etc. citrinin ergot alkaloids fumonisins Selected Properties and Actions four major types, B1 , B2 , G1 , and G2 ; associated with immune suppression, cancer of the liver and other organs particularly the lungs Penicillium citrinum, several Penicllium, and Aspergillus species contaminated corn, barley, oats, rice, rye, and wheat Claviceps species contaminated cereals two forms of disease states usually in the form of are recognized: convulsive bread which affects CNS, and gangrenous which affects blood supply to the extremities Fusarium species contaminated corn products yellow rice disease in Japan; highly toxic for nervous tissue in humans linked to esophageal cancer; harmful to agricultural products, and certain farm animals This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 72 THE MENACING FUNGI ochratoxin Aspergillus species contamination of barley, coffee, oats rye, wheat and other phenylalanine plant products; may be present in certain wines made from contaminated grapes Ochratoxin A; kidney and liver are major beans targets; interferes with metabolism; a problem for certain farm animals patulin Penicillium patulum and other Penicillium species contaminated unfermented apple juice toxic to both plants and animals trichothecenes Several fungal species including Fusarium, Stachybotrys, and Trichoderma contaminated food and feed products zeralenone a Fusarium graminearum contaminated cereal products direct contact causes dermatitis; ingestion causes vomiting, and abdominal and pulmonary bleeding causes increased estrogen production Kwashiorkor, a severe malnutrition disease, may be a form of aflatoxin poisoning in children. The Aflatoxins and Ergot Poisoning Aflatoxins are toxic metabolic products produced by the two molds Aspergillus flavus (Figure 15), and A. parasticus. Both species are fairly common fungi found in general, and are often found growing on various types of foodstuffs, which they are capable of decomposing and causing decay. In doing so, some species of Aspergillus produce aflatoxins. (The first part of the name for the mycotoxin is derived from using the A from the genus, and the fla from the species designations, respectively.) Two structural forms of aflaoxins are known, B and G types, of which the subtype aflatoxin B 1 is considered to be the most toxic. These mycotoxins have been found in various foods, including stored cereals, nuts such as peanuts, and hay and other forms of animal feed. There is also some evidence to indicate that aflatoxins were produced by Iraqi scientists as part of a bioweapons program during the 1980’s. Most of the toxin produced, some 2,300 liters, was used to fill warheads, with the remainder being stockpiled. There are no indications for the deployment of the warheads. The real and potential dangers of aflatoxin poisoning, also known as aflatoxicosis, was dramatically shown in 1960 when, by the occurrence of large-scale trout poisoning in commercial fish hatcheries, and concurrent outbreaks of turkey X disease in England. Both incidents were found to be caused by aflatoxins This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 73 THE MENACING FUNGI Although the risk to humans is unknown, there is significant evidence that aflatoxin contributes to liver cirrhosis, liver cancer, and can have immunosuppresive, embryonic and oncogenic effects. In parts of the world, such as India and portions of Africa, many people being treated for malnutrition may experience aflatoxin poisoning, because of poor storage facilities for the protein sources. Stored food items such as peanuts and cereals which often are used to correct malnutrition, also can serve as ideal nutrients for aflatoxin-producing fungi. Exposure to aflatoxins occurs primarily through the ingestion of contaminated foods. It should be noted that aflatoxin poisoning does not necessarily produce immediate effects upon ingestion. These poisons are stored in the liver, and depending on the amounts ingested may not produce disease for a long time. Severe, acute liver injury with high morbidity and mortality has been associated with high-dose exposures to aflatoxins. Ingestion of 2 to 6 milligrams/day of the mycotoxin for a month can cause acute hepatitis and death. Aflatoxins also can affect lower animals. These effects include miscarriages, stunting, and premature deaths of farm animals. Efforts to prevent aflatoxin poisoning include increased food inspections to detect the presence of aspergilli and to ensure food safety, local education and assistance to keep susceptible foods completely dry and properly stored. Ergot poisoning is caused by the mold Claviceps purpurea which attacks grain crops. Individuals become poisoned by ingesting rye or other cereal grains contaminated by this mold. The toxin is known to cause hallucinogenic effects and convulsions resulting in rather bizarre behavior similar to that described for individuals taking lysergic acid diethylamide (LSD). Ergot can also interfere with blood flow in the arms and legs which can result in local gangrene. The Sick-Building Syndrome The presence of mold on the internal surfaces of damp dwellings often results in a high airborne fungal spore count, which in turn, presents a distinct health risk to the occupants. Although these conditions tend to be principally of a respiratory nature, a prevalence of possible toxigenic signs and symptoms also have been reported. Causative Agents. The spores and mycelial fragments of a number of fungal species in high densities in buildings pose a potential health hazard from allergic reactions, and on some occasions, from infections. The presence of fungi producing mycotoxins may also contribute to adverse health effects called sick-building syndrome (SBS). Examples of fungal genera believed to be associated with SBS include Aspergillus, Fusarium, Penicillium, and Stachybotrys. Sources. The results of a number of studies involving analyses of indoor air samples, building materials, heating, ventilation, and air conditioning (HVAC) components, suggest that these environments and materials contribute to the fungal burden of indoor air under certain conditions. These studies emphasize that building materials including fiberglass duct liner and board, acrylic facing material, and painted metal vent surfaces of HVAC systems may be colonized by various fungal species. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 74 THE MENACING FUNGI Signs and Symptoms: Individuals living in damp, moldy housing may complain of such conditions as backache, blocked nasal passages, breathlessness, fainting, nausea, nervousness, and vomiting. Toxic-mold fears have precipitated a number of lawsuits. Unfortunately, much of the evidence is conjectural. Although the results of available studies have provided information regarding which microorganisms are present in the indoor environment, there are significant omissions, and sampling limitations and errors. For example, the presence of potential toxin-producing fungi does not necessarily imply the presence of mycotoxins, nor does the finding of mycotoxins prove that a particular fungus species is, or was present. While many fungal species can produce toxins (Table 14), the ability to produce toxins varies under particular environmental conditions. Often such “known” toxin producers will not make the toxic compounds. Moreover, while various fungal species, mycotoxins, and other microbial products have been implicated as causative agents of SBS, the range of signs and symptoms credited to these agents are greater than what can be explained rationally in terms of toxicological mechanisms. CONCLUDING STATEMENTS F ungi cause human illness in a variety of ways. Both the mycoses, which are the bestknown diseases caused by fungi, as well as the toxic metabolic products produced by some fungal species pose important health hazards. The danger is not only applicable to humans but, to a number of lower animals as well. The incidence of mycoses and mycotoxicoses may be more common than suspected. The successful diagnosis and appropriate treatment of these menacing diseases requires the coordination of the knowledge and the expertise of laboratory technologists and of clinical health care personnel treating patients. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 75 THE MENACING FUNGI GLOSSARY Terms analogue: a compound that is structurally similar to another antibody: a protein molecule formed in response to, and interacting specifically with an antigen; also known as immunoglobulin antigen: a substance that causes the formation of antibodies (immunoglobulins) bronchopleural fistula: an abnormal tube-like passage involving the bronchi and pleura cavity cavitation : cavity formation CD4 cell: a lymphocyte component of the immune system that signals other cells of this system to perform their respective functions; this cell type is HIV’s target for infection Cushing’s syndrome: a condition resulting from abnormal hyper-secretion of adrenal cortex hormones empyema: pus in a body cavity hemoptysis: the spitting of blood arising from the mouth, voice box, trachea, bronchi, or lungs hypha: the microscopic threadlike structural unit of molds; forms the structure of the fungus colony or mycelium immunoglobulin: a glycoprotein molecule that reacts specifically with the substance and/or cells that caused its formation; also known as antibody mycelium: the fungal colony nosocomial: refers to hospital acquired infections PCR: polymerase chain reaction assay; a laboratory method for measuring circulating antigens or antibodies associated with a disease and/or foreign agent pyopneumthorax: the presence of pus and gas in the pleural cavity This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 76 THE MENACING FUNGI sarcoidosis: a disease of unknown cause resulting in the formation to tubercle-like lesions that may occur in any body organ sign: any objective evidence or manifestation of an illness or disease state symptom: any subjective perceptible change in the body or its functions that indicates disease or a form or phases of diseases This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 77 THE MENACING FUNGI SUGGESTED READING AND REFERENCES Alangaden, G.J., et al., “Aspergillosis: the Most Common Community-Acquired Pneumonia with Gram-Negative Bacilli As Copathogens in Stem Cell Transplant Recipients with GraftVersus-Host Disease”. Clinical Infectious Disease. 35:659-664; 2002;. Bennett, J.W. and M. Klich. “Mycotoxins.” Clinical Microbiology Reviews. 16:497-516; 2003. Denning, D.W., et al., “Efficacy and Safety of Viriconazole in the Treatment of Acute Invasive Aspergillosis.” Clinical Infectious Disease. 2002; 34:563-571. Johnson, P.C., et al., “Safety and Efficacy of Liposomal Amphotericin B Compared with Conventional Amphotericin B for Induction Therapy of Histoplasmosis in Patients with AIDS.” Annals of Internal Medicine. 137: 105; 2002. Kuberski, T.T., et al., “Successful Treatment of a Critically Ill Patient with Disseminated Coccidioidomycosis, Using Adjunctive Interferon-gamma.” Clinical Infectious Diseases. 38: 910, 2004. Kuhn, D.M. and M.A. Ghannoum. “Indoor Mold, Toxigenic Fungi, and Stachybotrys chartarum: Infectious Disease Perspective.” Clinical Microbiology Reviews. 16:144-172; 2003. Masur, H. et al., “Introduction to the 1999 USPHS/IDSA Guidelines for the Protection of Opportunistic Infections in Persons Infected with Human Immunodeficiency Virus.” Clinical Infectious Diseases. 30: S1, 2000. McNeil, N.M. and N.M. Ampel. “Opportunistic Coccidioidomycosis in Patients Infected with Human Immunodeficiency Virus: Prevention Issues and Priorities.” Clinical Infectious Diseases. 21 (Supplement 1): 111, 1995. Mocheria, S. and L.J. Wheat. “Treatment of Histoplasmosis.” Seminars in Respiratory Infections. 16:141; 2001. Stoodley, P. et al., “Biofilms As Complex Differentiated Communities.” Annual Review of Microbiology. 56; 187-209; 2002. Tobon, A.M, et al., “Residual Pulmonary Abnormalities in Adult Patients with Chronic Paracoccidioidomycosis: Prolonged Follow-up after Itraconazole Therapy.” Clinical Infectious Disease. 2003; 37:898-904. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 78 THE MENACING FUNGI POST TEST DIRECTIONS: IF COURSE WAS MAILED TO YOU, CIRCLE THE MOST CORRECT ANSWERS ON THE ANSWER SHEET PROVIDED AND RETURN TO: RCECS, 16781 VAN BUREN BLVD, SUITE B, RIVERSIDE, CA 92504-5798 OR FAX TO: (951) 789-8861. IF YOU ELECTED ONLINE DELIVERY, COMPLETE THE TEST ONLINE – PLEASE DO NOT MAIL OR FAX BACK. 1. Which of the following terms refers to the number of individuals within a population who develop a specific disease during a particular time period? a. b. c. d. e. frequency epidemic sporadic condition incidence pandemic 2. If a particular disease suddenly affects large numbers of people in different parts of the world would be considered as being which of the following? a. b. c. d. e. endemic frequent epidemic pandemic sporadic 3. The fuzzy, cottony, threadlike network of a fungus that is visible to the eye is specifically called which of the following? a. b. c. d. e. mold conidia hypha mycelium yeast 4. Which of the following choices gives the term for the capacity of a fungus to exhibit both yeast and mold phases? a. b. c. d. e. asexual reproduction sexual reproduction dimorphism choices a and b only none of these This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 79 THE MENACING FUNGI 5. Which of the following fungal diseases is an example of a superficial mycosis? a. b. c. d. e. ringworm Candida albicans infection histoplasmosis sporotrichosis coccidioidomycosis 6. Which of the following fungal diseases is an example of a subcutaneous mycosis? a. b. c. d. e. tinea pedis Candida albicans infection histoplasmosis sporotrichosis coccidioidomycosis 7. Which of the following choices represent the means by which humans can acquire Blastomyces dermatitidis? a. b. c. d. e. ingestion of contaminated food or drink conidia-infected fleas tick bites inhalation of conidia from mycelia growing in soil infected person-to-person contact 8. Which of the following choices lists the CURRENTLY RECOGNIZED causative agents of San Joaquin Valley fever? a. b. c. d. e. Candida albicans and C. immitis Blastomyces dermatitidis and C immitis Coccidioides immitis and C. posadasii Paracocidioides brasiliensis and C. posadasii Coccidioides immitis and Paracocidioides brasiliensis 9. Which of the following animals are generally NOT susceptible to C. immitis infection? a. b. c. d. e. cattle dogs birds horses sheep This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 80 THE MENACING FUNGI 10. Which of the following choices is NOT CORRECT in the case of coccidioidomycosis? a. b. c. d. e. coccidioidomycosis is not contagious coccidioidomycosis can be spread from person-to-person about 40 percent of cases are symptomatic about 40 percent of cases are asymptomatic most infected persons exhibit typical flu-like symptoms 11. C. immitis spores would generally NOT BE found in which of the following areas? a. b. c. d. e. San Joaquin Valley of California Alaska southern portions of Arizona parts of Central America such as Guatemala, and Honduras countries of South America including Venezuela, Columbia, Paraguay, and Argentina 12. Coccidioidomycosis generally results from which of the following? a. b. c. d. e. the ingestion of C. immitis spores tick bites earthquakes the inhalation of C. immitis spores fomites (contaminated inanimate objects) 13. Which of the following materials is used in skin tests to determine an exposure and/or the sensitivity (hypersensitivity or allergy) of individuals to C. immitis? a. b. c. d. e. tuberculin purified protein derivative coccidioidin C. immitis arthrospores None of these 14. Which of the following conditions is the MOST FREQUENT complication of primary coccidioidomycosis? a. b. c. d. e. chronic pulmonary cavitation coccidioidoma bronchiectasis pulmonary fibrosis pneumothorax This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 81 THE MENACING FUNGI 15. A negative skin test for C. immitis MAY NOT indicate which of the following conditions? a. b. c. d. the test was performed too early in the disease process the current illness in the patient is not the disease being tested for previous exposure to C. immitis a case of disseminated coccidioidomycosis in which the individuals immune response has been impaired e. choices a and d only 16. Which of the following types of individuals WOULD NOT be a likely victim of histoplasmosis? a. b. c. d. e. spelunkers (cave explorers) farmers sailors construction workers heating and/or air conditioning service personnel 17. Histoplasmosis generally results from which of the following? a. b. c. d. e. the ingestion of H. capsulatum spores tick bites the inhalation of H. capsulatum spores dog bites fomites (contaminated inanimate objects) 18. Which of the following materials is used in skin tests to determine an exposure and/or the sensitivity (hypersensitivity or allergy) of individuals to H. capsulatum? a. b. c. d. e. tuberculin histoplasmin purified protein derivative coccidioidin H. capsulatum macroconidia This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 82 THE MENACING FUNGI 19. When procedures for the removal of infectious soil containing bat or bird fecal matter and H. capsulatum are impractical, which of the following choices lists a suitable approach for effective soil decontamination? a. b. c. d. e. periodic water sprays applied to the involved area covering the area with sterilized soil allow the material to decay with time the application of formaldehyde solutions to treat contaminated areas either choice a or c only 20. Aflatoxins usually MAY NOT be associated with which of the following? a. b. c. d. e. nuts cereals mushrooms animal feed none of the above 21. Which of the following choices BEST DESCRIBES the main portal of entry and site for Aspergillus fumigatus infections? a. b. c. d. e. gastrointestinal tract kidneys skin respiratory tract bones 22. Which of the following choices lists the MOST COMMON cause of nosocomial Candida albicans infections? a. b. c. d. e. ingestion of contaminated food or water infectious flies yeast normally found in the body’s microbial (endogenous) population direct contact with lesions in other individuals through sexual intercourse 23. The microscopic finding of yeast cells and/or pseudohyphae in infected tissue or body fluid specimens would suggest an infection of which of the following fungi? a. b. c. d. e. Histoplasma capsulatum Aspergillus fumigatus Crytococcus neoformans Coccidioides immitis Candida albicans This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 83 THE MENACING FUNGI 24. Which of the following choices lists a disease state considered in the United States as an AIDS-defining condition? a. b. c. d. e. paracococcidiomycosis coccidioiomycosis Candida albicans-caused esophagitis histoplasmosis aflatoxin poisoning 25. Which of the following is INCORRECT with respect to biofilms? a. a significant proportion of human infections involve biofilms formed by microorganisms b. microbial biofilms develop when microorganisms adhere to a surface and produce extracellular polymers of carbohydrates, or proteins, that provide a matrix and aid in further attachments c. microorganisms in biofilms do not behave differently from freely suspended microbes d. both bacteria and Candida species within biofilms are markedly resistant to antimicrobial agents e. biofilm-associated infections with retained medical devices may recur after cessation of antibiotic therapy and may require device removal.. 26. Which of the following structures an/or components associated with Cryptococcus neoformans is unique among pathogenic fungi and contributes to the disease producing capability of the pathogen by interfering with host immune processes such as phagocytosis? a. b. c. d. e. individual cells pseudohyphae mycelium cell wall capsule 27. Cryptococcus neoformans is normally acquired by humans by which of the following? a. b. c. d. e. ingestion of contaminated food or water through inhalation of the pathogen infected tick bites infected bats choices c and d only This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 84 THE MENACING FUNGI 28. Which of the following choices would likely be the original location of P. marneffei infections? a. b. c. d. e. San Joaquin Valley of California Certain countries in Southeast Asia Alaska southern portions of Arizona countries of South America including Venezuela, Columbia, Paraguay, and Argentina 29. Penicilliosis generally results from which of the following? a. b. c. d. e. the ingestion of P. marneffei spores tick bites infected mosquitoes the inhalation of P. marneffei spores fomites (contaminated inanimate objects) 30. Which of the following choices lists the two MAJOR consequences of ergot poisoning? a. b. c. d. e. convulsions and gangrenous ergotism of the extremities meningitis and cutaneous ergotism immune suppression and dermatitis sick-building syndrome and bleeding bleeding and vomiting GW: Test Version A This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 85 THE MENACING FUNGI ANSWER SHEET NAME____________________________________ STATE LIC #_______________________ ADDRESS_________________________________ AARC# (if applic.)___________________ DIRECTIONS: (REFER TO THE TEXT IF NECESSARY – PASSING SCORE FOR CE CREDIT IS 70%). IF COURSE WAS MAILED TO YOU, CIRCLE THE MOST CORRECT ANSWERS AND RETURN TO: RCECS, 16781 VAN BUREN BLVD, SUITE B, RIVERSIDE, CA 92504-5798 OR FAX TO: (951) 789-8861. IF YOU ELECTED ONLINE DELIVERY, COMPLETE THE TEST ONLINE – PLEASE DO NOT MAIL OR FAX BACK. 1. a b c d e 16. a b c d e 2. a b c d e 17. a b c d e 3. a b c d e 18. a b c d e 4. a b c d e 19. a b c d e 5. a b c d e 20. a b c d e 6. a b c d e 21. a b c d e 7. a b c d e 22. a b c d e 8. a b c d e 23. a b c d e 9. a b c d e 24. a b c d e 10. a b c d e 25. a b c d e 11. a b c d e 26. a b c d e 12. a b c d e 27. a b c d e 13. a b c d e 28. a b c d e 14. a b c d e 29. a b c d e 15. a b c d e 30. a b c d e GW: Test Version A This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 86 THE MENACING FUNGI EVALUATION FORM NAME:____________________________________________ DATE:______________ AARC # (if applic.)________________________ STATE LICENSE #:______________ RC Educational Consulting Services, Inc. wishes to provide our clients with the highest quality CE materials possible. 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