SEM421: MYCOLOGY ROYMARK S. CABAHUG, RMT Mycology +the discipline of biology that describes and studies a very vast group of organisms denominated fungi. Mycology +the branch of biology concerned with the study of fungi, including their taxonomy, genetics, biochemical properties, and use by humans. +Mycology branches into the field of phytopathology, the study of plant diseases. Mycology + The two disciplines, are closely related, because the vast majority of plant pathogens are fungi. + This group contains around 90,000 species, and thousands are described every year, being estimated that there might be more than one million fungal species in the world, which makes the fungal kingdom one of the most important in the tree of life. + A biologist specializing in mycology is called a mycologist. Mycology +Comes from the Ancient Greek: μύκης (mukēs), meaning "fungus" and the suffix -λογία (-logia), meaning "study.“ Prokaryotes +Sometimes spelled as Procariote Prokaryotes +A microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles. + Includes the bacteria and archaea, which scientists believe have unique evolutionary lineages. Prokaryotes + Small, single-celled organisms that have a relatively simple structure. + Are surrounded by a plasma membrane, but they have no internal membrane-bound organelles within their cytoplasm. + The absence of a nucleus and other membrane-bound organelles differentiates prokaryotes from another class of organisms called eukaryotes. Eukaryotes +Eukaryotes constitute the domain of Eukaryota or Eukarya. +An organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus. +Include all living organisms other than the bacteria and archaea. Eukaryotes +Are organisms whose cells have a membrane-bound nucleus. +All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. Archaea - Is a domain of organisms. - Are single-celled microorganisms with structure similar to bacteria. - Bacteria can cause illnesses, archaeans do not. Archaea - Traditionally, Archaea only included its prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are now known to have evolved from archaea. Fungi + Historically, the fungi were regarded as relatively insignificant causes of infection. +Can be a source of tinder, food, traditional medicine, as well as entheogens, poison, and infection. +Constitute an extremely diverse group of organisms and are generally classified as molds or yeasts. Fungi +Are eukaryotic. Fungi + They possess a true nucleus, with a nuclear membrane and mitochondria. + Some have been recognized as classic pathogens, whereas others are recognized only as environmental saprobes, living on nonliving material. + decompose organic waste and are essential for recycling of carbon and minerals in our ecosystem. Fungi +Lacks chlorophyll and must absorb nutrients from the environment. +Cell walls are made of chitin, whereas those of plants contain cellulose. Fungi +Most fungi are obligate aerobes that grow best at a neutral pH, although they tolerate a wide pH range. +Moisture is necessary for growth, but spores and conidia survive in dry conditions for extended lengths of time. +Gram positive and require oxygen to survive. Fungi + Contains a nucleus bound by a membrane, endoplasmic reticulum, and mitochondria. + Heterotrophic like animals and most bacteria. + They require organic nutrients as a source of energy, while plants are autotrophic. Fungi +Are dependent upon enzymes systems to derive energy from organic substrates. Fungi +Are essential in recycling of elements, especially carbon. Nucleus + As related to genomics, is the membrane-enclosed organelle within a cell that contains the chromosomes. + In a cell, an array of holes, or pores, in the nuclear membrane allows for the selective passage of certain molecules (such as proteins and nucleic acids) into and out of the nucleus. + The nucleus is one of the most obvious parts of the cell when you look at a picture of the cell. Nucleus +In biology, the structure in a cell that contains the chromosomes. +It's in the middle of the cell, and the nucleus contains all of the cell's chromosomes, which encode the genetic material. spores +Are microscopic biological particles that allow fungi to be reproduced, serving a similar purpose to that of seeds in the plant world. Conidia +A spore originating from a conidiophore by the formation of a delimiting septum. +Microscopic asexual spores produced by molds +The main means of propagating many species. Conidiophore +A special hypha +The conidiophores arise singly or in loose groups, erect, straight, or somewhat flexuous, mostly simple but occasionally branched. septate, and scarcely swollen at the tip, with meristematic apices capable of producing conidia in basipetal succession to form characteristic chains. Ascospores +are the sexually produced fungal spore formed within an ascus, produced after growth on ascospore agar. Hypha +Comes form the Greek word “Hyphae” which means “Web” +A long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. +Consists of one or more cells surrounded by a tubular cell wall. Chlorophyll +a pigment that gives plants their green color, and it helps plants create their own food through photosynthesis. +a key component in the process of photosynthesis, which sustains plant life and produces oxygen for the entire planet. Molds +exhibit filamentous type of growth +filamentous fungi with small fruiting bodies Yeasts +pasty or mucoid form of fungal growth +are among the most heavily utilized members of the Kingdom Fungi, particularly in food manufacturing. Toadstool +any of various inedible or poisonous species of mushrooms. Saprobes +Are the group of fungi that act as decomposers, feeding on dead and decaying wood, leaves, litter, and other organic matter. +To digest this, they secrete enzymes that break it down. +This releases and recycles vital nutrients for other organisms, and helps dispose of organic waste Saprobes +This decomposers are essential for the survival of ecosystems. Fungal Infections +Also known as Mycosis. +Any disease or condition you get from a fungus. dermatophytes • Cannot grow at 37C • Genera in this group include Trichophyton, Microsporum, and Epidermophyton. • A ringworm inflammation at advancing margin of dry, scaly lesion without inflammation dermatophytes • itching, scaling, or ringlike patches of the skin, brittle, broken hairs, and thick, discolored nails, Athlete’s foot, jock itch • Keratinophilic, which means it affects hair, nails, and cutaneous layers of skin that contain the scleroprotein keratin) • These dermatophytes affect keratinized structures such as hair and the epidermis' stratum corneum resulting in a characteristic rash. dermatophytes • Asexual conidia: reproductive cells: macroconidium or microconidium is commonly observed • Sexual conidia: reproductive cells: ascospores rarely observed • Mycosel medium or Mycobiotic medium: 1-3 weeks dermatophytes • Zoophilic: animals • Anthropophilic: human hosts • Geophilic: soil dermatophytes • They do not invade subcutaneous or deep tissues. dermatomycosis • fungal diseases of the keratinized tissues of humans and other animals. • is the medical term for fungal infections of the skin and skin appendages which encompass nails and hair. • derma: skin, mykes: fungus dermatomycosis + Fungal infection can happen any time there are injured or pathologically changed skin areas. + However, there are also factors which may promote fungal infections of healthy skin areas. + Warm, humid areas such as feet, spaces between toes, and armpits are often colonised by fungi. dermatomycosis +Due to the warm and humid environment, the conditions are optimal for the reproduction of the pathogens. +Moreover, the skin is more sensitive, enabling the pathogens to enter the skin more easily. Cosmopolitan +Means including or containing people from many different countries. Humid +It contains a high amount of water or water vapor; noticeably moist; humid air; a humid climate. +Containing or characterized by perceptible moisture especially to the point of being oppressive Skin Appendages +Are epidermal and dermal-derived components of the skin that include hair, nails, sweat glands, and sebaceous glands. +include sweat glands, nails, and the pilosebaceous unit of the skin, comprised of the hair shaft, hair follicle, sebaceous gland, and arrector pili muscle — these appendages derive from a down growth of the epidermis beginning in the third month of fetal life. Hair Follicles +Are part of your skin that are responsible for growing your hair Scalp +The is the area of the head where head hair grows. +The average human scalp contains 100,000 hairs Skin Rashes +Can be red, inflamed, bumpy as well as dry, itchy or painful. Lesion +is a region in an organ or tissue which has suffered damage through injury or disease, such as a wound, ulcer, abscess, or tumor. +A lesion caused by fungi, also known as a mycosis, can appear as a red, swollen, or bumpy rash on the skin. Verrucous Lesions +are defined as “pertaining to or marked by wart like growth pattern.” Toe Web Infection (TWI) +Is a bacterial infection of the interdigital space. Fungal Sinusitis +Affects paranasal sinuses +A rare infection in healthy individuals but is relatively common in immunocompromised patients. Tuberculosis (TB) +An infectious disease caused by bacteria that most often affects the lungs. Chronic Granulomatous (CGD) +An inherited disorder that occurs when a type of white blood cell, called a phagocyte, doesn't work properly. Self-Limited Diseases +Or infections are those that resolve spontaneously, with or without specific treatment Type of Hair Fungal Invasion +Ectothrix +Endothrix Ectothrix +is a chronic inflammatory dermatophytosis, characterized by scutula formation. Endothrix +Refers to dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell. En Grappe +Means in clusters Echinulate +Set with small spines or prickles Species / causative agents • Infections Involving Hair Follicle • Causes Tinea favosa, or favus • crusty lesion Trichophyton schoenleinii • a fungus in the family Arthrodermat aceae • causes ringworm infection of the scalp. • endothrix hair involvement Trichophyton tonsurans • Replaces the Microsporum audounii as the leading cause of scalp infection • Causes tinea unguium Trichophyton tonsurans • Causes black dot ringworm • May be identified through analysis of its fast-growing colonies. • Microconidia: round peg shape, miniature balloon appearance Trichophyton tonsurans + An anthropophilic, cosmopolitan dermatophyte. + are common causes of tinea capitis in parts of Africa and West Asia, have only rarely been reported to cause dermatophytoses in the United States. Trichophyton violaceum + endemic in Africa +Endothrix hair involvement Trichophyton violaceum +Primarily causes tinea capitis and less commonly tinea corporis and tinea unguium. • Causes Black Dot Tinea Capitis • Causes tinea pedis, tinea corporis & tinea capitis Trichophyton rubrum • A typical microscopic picture of T. rubrum contains clavate- or peg- shaped microconidia formed along undifferentiated hyphae Trichophyton rubrum • Colonies are Downy or granular form or sugar sprinkled medium appearance. • Causes tinea pedis, tinea capitis, tinea corporis, tinea barbae, tinea cruris, tinea unguium. • Hair: Ectothrix Trichophyton mentagrophytes • Microconidia are primarily globose but may appear tearshaped en grappe • Macroconidia are thinwalled, smooth, and cigar-shaped, with four to five cells separated by parallel cross walls. • Spiral hyphae Trichophyton mentagrophytes • Granular colonies are noted when abundant microconidia are formed. • Causes Tinea pedis • Clonal line within sexual species T. mentagrophytes. Trichophyton interdigitale • Found in cattle • Tinea corporis, tinea capitis, tinea barbae • Ectothrix Trichophyton verrucosum Trichophyton verrucosum +Grows well at 35C • an anthropophilic fungus in the genus Microsporum. • a type of dermatophyte that colonizes keratinized tissues, primarily hair, causing infection. Microsporum audouinii • characterized by its spindle-shaped macroconidia Microsporum audouinii • outer portion of hair shafts: ectothrix • causes the infections Tinea capitis and Tinea corporis. • responsible for most of the gray patch tinea capitis of children Microsporum audouinii • an anthropophilic fungus in the genus Microsporum. • Anthropophilic • initially described by Ota in 1921 as a dermatophyte causing Tinea capitis in Japan and surrounding areas • strains were occasionally identified although this dermatophyte is difficult to differentiate from Microsporum audouinii or Microsporum canis. Microsporum ferrugineum Microsporum ferrugineum • Common causes the infections Tinea capitis. • outer portion of hair shafts: ectothrix • Hyphae with thick septa “bamboo” hyphae Microsporum ferrugineum • May form both macro- and microconidia, although they are not always present. • Geophilic • Causes tinea barbae • Ectothrix Microsporum gypseum Microsporum gypseum • The fusiform, moderately thick-walled conidia typical of Microsporum gypseum can have as many as six cells. • Spindle shape spores with 4-6 septa • In some isolates, the distal end of the macroconidium might bear a thin, filamentous tail. Microsporum gypseum • Cinnamon color, powdery, granular appearance on colony surfaces. • New name: Nannizzia gypsea • With pleomorphic tufts of white sterile hyphae • Macroconidia: spindle-shaped, with echinulate, thick walls; have 3 to 15 cells • Spiny distal ends of the macroconidia are key features that distinguish this species. • Colonies are fluffy and white, with the reverse side of the colony usually developing a lemon yellow/rich canary yellow pigment, especially on potato dextrose agar. Microsporum canis • Causes Tinea Pedis, Tinea Unguium • Macroconidia: club shaped Epidermophyton floccosum • The distal end of the conidium is broad or spatulate and reminiscent of a beaver’s tail. Disease / infections Ringworm Infection - It gets its name because of its circular appearance. Tinea favosa • Forms a crusty lesion • Crusty, cup-shaped flakes called scutula are formed. • Hair loss and scar tissue formation Tinea capitis • Aka scalp ringworm • a chronic fungal infection of the scalp occurring commonly in children of school age, especially in developing countries. • Symptoms of tinea capitis include swollen red patches, dry scaly skin rashes, itchiness and hair loss. Tinea capitis • Mold-like fungi called dermatophytes causes this. • It is caused primarily by the dermatophyte members of genera Microsporum and Trichophyton. • luster and color of the hair shaft may be lost Tinea capitis • is of public health importance because of its transmissibility. • 2 types: Gray Patch Ringworm and Black Dot Ringworm • Causes Gray Patch Ringworm in children Tinea capitis +Treatment for a tinea capitis infection involves the use of an oral antifungal medication. Black dot ringworm +A type of tinea capitis +hair shafts: brittle, break off at the scalp, leaving the black dot stubs tinea unguium • Also known as Onychomycosis • Terbinafine or Itraconazole is considered the best treatment • Subungual is the most common form of onychomycosis, described as lateral, distal, or proximal. tinea unguium • Infections involving the nails Tinea Pedis • Also known as Athlete’s foot • A common disease • affects the soles of the feet and toe webs Tinea Pedis oIn more severe cases, the sole of the foot may develop extensive scaling, with fissuring and erythema. oThe disease may progress around the sides of the foot from the sole, giving rise to use of the term moccasin foot. oPatients contract the infection by directly contacting the organism while walking barefoot. Tinea Pedis - fungal skin infection that usually begins between the toes. Tinea corporis + Ringworm of the body + a rash caused by a fungal infection + It's usually an itchy, circular rash with clearer skin in the middle. Tinea corporis +Is the infection of the glabrous skin Tinea barbae + Beard ringworm. + A fungal infection most commonly found in animals like cows causes this infection to people. + The condition causes red, ring-shaped skin rashes. Tinea cruris + also known as jock itch + is an infection involving the genital, pubic, perineal, and perianal skin caused by pathogenic fungi known as dermatophytes. + Is a fungal skin infection that causes an itchy rash in warm, moist areas of the body. Tinea cruris +Rash often affects the groin and inner thighs and may be shaped like a ring. tests Growth on Rice Grains • Sterile, nonfortified rice is inoculated lightly with a portion of a colony. • After 10 days of incubation at room temperature, the medium is observed for growth. • M. canis and almost all other dermatophytes grow well and usually form many conidia Growth on Rice Grains + M. audouinii does not grow but turns the rice grains brown. Hair Perforation Test +Also known as Modified Hair Baiting Test +5- to 10-mm sterile hair fragments are floated on sterile water supplemented with a few drops of sterile 10% yeast extract. +Conidia or hyphae from the dermatophyte in question are inoculated onto the water surface. Hair Perforation Test +Hair shafts are removed and microscopically examined in LPCB at weekly intervals for up to 1 month. + T. rubrum: causes only surface erosion of hair shafts Urease Test + Another test used to help differentiate T. mentagrophytes from T. rubrum is the 5day urease test. + Tubes of Christensen urea agar are very lightly inoculated with the dermatophyte and held for 5 days at room temperature. + T. mentagrophytes: urease production, resulting in a color change of the medium from peach to bright fuchsia Urease Test + T. rubrum: isolates are negative or require more than 5 days to give a positive reaction SUBCUTANEOUS MYCOSES Subcutaneous Layer +the deepest skin layer. +It protects a person’s body and keeps it warm. SUBCUTANEOUS MYCOSES + Subcutaneous fungal infections often result from a traumatic skin puncture from thorns or vegetation contaminated with fungi. + These fungi are found as saprobes in the soil or as plant pathogens. + Because the subcutaneous tissue is affected, there is a host immune response from macrophages, neutrophils, lymphocytes, and other cells. SUBCUTANEOUS MYCOSES + May disseminate to other sites, and these infections often become chronic. + There are four major groups of subcutaneous fungal infections, it includes the chromoblastomycosis, mycetoma, phaeohyphomycosis, and sporotrichosis. + deeper skin layers, including muscle, connective tissue, and bone SUBCUTANEOU S MYCOSES +progressive, nonhealing ulcers and the presence of draining sinus tracts. +include a heterogeneous group of fungal infections that develop at the site of transcutaneous trauma. Chromoblastomycosis Chromoblastomycosis (CBM) + caused by infection with dematiaceous fungi, a group of dark, slowgrowing fungi that are found on vegetation and in the soil. + Clinically significant fungi in this group include Fonsecaea pedrosoi, Fonsacaea compactum, Phialophora verrucosa, Cladosporium carrionii, Exophiala jeanselmi, Exophiala spinifera, and Wangiella dermatitidis. + Infection is initiated through a puncture wound or trauma to the skin involving fungally contaminated vegetation. Chromoblastomycosis (CBM) +A local infection in the underlying tissue results, with the development of chronic, nonhealing, hard, warty, tumor-like lesions. +The infection most frequently involves the feet and lower legs. +Although chromoblastomycosis has a worldwide prevalence, it is seen most often in the tropics. Chromoblastomycosis (CBM) +Also known as verrucous dermatitidis. +Lesions of Chromoblastomycosis has verrucous nodules that may become ulcerated and crusted. Fonsecaea pedrosoi + The species most frequently found worldwide as a major etiologic agent of chromoblastomycosis. + The colonies are very slow growing with olive, gray, or black colonies that have a velvety texture. + It shows mixed sporulation, with a predominance of primary conidia forming at the tips of conidiophores arising from dark, septate hyphae. Fonsecaea pedrosoi + a fungal disease whose pathogenic events are poorly understood. + treatment of the disease presents poor effectiveness and serious side effects. + the disease is epidemiologically important in several regions, which has stimulated studies focused on the biology and pathogenic potential of its major causative agent. Fonsecaea pedrosoi +a fungal species in the family Herpotrichiellaceae. +species is commonly found in tropical and sub-tropical regions, especially in South America, where it grows as a soil saprotroph +Farming activities in the endemic zone are a risk factor for the development of chromoblastomycosis. Phialophora verrucosa + Rapidly grows producing olive gray to black cottony or wooly colonies. + Microscopically, Phialophora has septate hyphae with short conidiophores with flask-shaped phialides with collarettes + Oval to cylindrical conidia form clusters at the ends of the phialides. Phialophora verrucosa +Its macroconidia has vase-like structures. +a pathogenic, dematiaceous fungus that is a common cause of chromoblastomycosis. +reported to cause subcutaneous phaeohyphomycosis and mycetoma in very rare cases. Phialophora verrucosa + In the natural environment, it can be found in rotting wood, soil, wasp nests, and plant debris. + Sometimes referred to as Phialophora americana, a closely related environmental species which, along with P. verrucosa, is also categorized in the P. carrionii clade. + The P. verrucosa was first isolated by Edgar Mathias Medlar in 1915 from a chronic skin lesion on the buttock of a 22-year-old man in Boston, Massachusetts who presented with verrucous lesions on the buttocks and feet. Phaeohyphomycosis Phaeohyphomycosis + Refers to infections caused by any dematiaceous fungi, excluding chromoblastomycosis and mycetoma. + These fungi are darkly pigmented with septate hyphae + Fungi associated with phaeohyphomycosis include Bipolaris, Curvularia, E. jeanselmi, Phialophora richardsiae, and W. dermatitidis. Phaeohyphomycosis +Caused by fungi that have melanin in their cell walls. Curvularia spp. + Rapidly grows white to pink woolly colonies, which darken in color to brown or black with age. + Microscopically, there are brown septate hyphae and branched or straight conidiophores with pyriform, brown multiseptate conidia. + Each cell is divided into multiple cells by the septum, and because the central cell is darker and larger, Curvularia has a curved shape Curvularia spp. +The genus Curvularia contains about 80 species, which are mostly soil or plant pathogens. Wangiella spp. + a dark, budding yeast and later develops tube-like phialides and groups of single-celled hyaline conidia. +Order: Chaetothyriales Mycetoma Mycetoma + a disease caused by certain types of bacteria and fungi found in soil, plant matter, and water + A chronic granulomatous infection of the cutaneous and subcutaneous tissue and bone. + There are tumor-like deformities of the subcutaneous tissue with abscesses, draining sinuses, and granulomatous pus. Mycetoma + includes Actinomycotic mycetoma and Eumycotic mycetoma. + a localized chronic, suppurative, and deforming granulomatous infection seen in tropical and subtropical areas. + characterized by a progressive and chronic granulomatous infection affecting the skin and subcutaneous tissue. Actinomycotic mycetoma + results from infection with the aerobic Actinomyces, such as Nocardia, Actinomadura, and Streptomyces. Eumycotic mycetoma + associated with several fungal species that have septate hyphae, including Pseudoallescheria, Aspergillus, Exophiala, Acremonium, Curvularia, and Madurella. + a deep fungal infection of the skin and subcutaneous tissue commonly caused by the filamentous fungi Madurella mycetomatis. Sporotrichosis Sporothrix schenckii + the agent of sporotrichosis, a subcutaneous infection, is categorized as a dimorphic fungus and exhibits both a yeast phase and a mycelial phase. + Sporotrichosis most often occurs from a skin trauma caused by a finger prick from thorny plants, such as roses. + The infection may remain local or cutaneous but is usually subcutaneous. Sporothrix schenckii +Associated with gardening, particularly with exposure to rose thorns and sphagnum moss. Media Leonian’s Agar +Used for stimulating pycnidium formation in Sphaeropsidales. Modified Leonian’s Agar +Used to culture Fonsecaea pedrosoi Systemi c Fungi Sir RM Systemic Fungi oSystemic Mycoses oAre dimorphic fungi, which exhibit both a yeast phase and a mycelial phase. oThe yeast phase is found within the host tissues and also is known as the tissue or invasive phase. Systemic Fungi oThe mycelial, or mold, phase is saprophytic and exists in nature on vegetation or decaying material; it is usually observed in vitro. Systemic Fungi o are identified by growth characteristics, colonial morphology, and microscopic characteristics of the conidia and hyphae. o Exoantigen testing also may be helpful in the serological identification of the dimorphic fungi, soluble antigens are extracted from the mycelial elements of the fungi to be identified. Systemic Fungi oMost systemic fungal infections are caused by opportunistic fungal pathogens in im munocompromised hosts. Systemic Fungi oHowever, invasive disease can occur in immunocompetent individuals if the exposure dose is high or with primary or dimorphic fungal pathogens which is a cause of endemic mycoses include Blastomyces, Coccidio ides, Histoplasma, Paracoccidioides an d Talaromyces spp. Systemic Fungi oMany pathogenic fungi are dimorphic, forming molds at ambient temperatures but yeasts at body temperature. oA group of fungal infections that affect multiple organs or tissues in the body, leading to serious and potentially life-threatening illnesses. Systemic Mycoses +Are infections that can occur in both immunocompromised and immunocompetent individuals and are caused by a variety of fungal pathogens. Species of Systemic Fungi o Blastomyces dermatitidis o Coccidioides immitis o Coccidioides posadasii o Histoplasma capsulatum o Paracoccidioides brasiliensis o Penicillium marneffei o Cryptococcus neoformans Blastomyces dermatitidis othe causal agent of blastomycosis. oinfections may be mild and asymptomatic or severe and chronic. othe infection is acquired through inhalation of the conidia or hyphae. Blastomyces dermatitidis o The organism appears in tissue or body fluids on direct microscopic examination as round to oval yeast cells with thick-walled, broad-based, single budding. o a dimorphic fungus, an invasive and often serious fungal infection found occasionally in humans and other animals. o It lives in soil and wet, decaying wood, often in an area close to a waterway such as a lake, river or stream. Blastomyces dermatitidis o Indoor growth may also occur, for example, in accumulated debris in damp sheds or shacks. o Endemic to parts of eastern North America, particularly boreal northern Ontario, southeastern Manitoba, Quebec south of the St. Lawrence River, parts of the U.S. Appalachian mountains and interconnected eastern mountain chains, the west bank of Lake Michigan, the state of Wisconsin, and the entire Mississippi Valley including the valleys of some major tributaries such as the Ohio River. o In addition, it occurs rarely in Africa both north and south of the Sahara Desert, as well as in the Arabian Peninsula and the Indian subcontinent. Blastomyces dermatitidis o Though it has never been directly observed growing in nature, it is thought to grow there as a cottony white mold, similar to the growth seen in artificial culture at 25 °C or 77 °F. o In an infected human or animal, however, it converts in growth form and becomes a large-celled budding yeast. o The sexual form of this Blastomyces dermatitidis was formerly known as Ajellomyces dermatitidis. Blastomyces dermatitidis oa thermally dimorphic fungus. ofrom the Kingdom “Fungi” oIn 2013, a second species was described in the genus Blastomyces, the B. gilchristii, which subsumes certain strains previously assigned to B. dermatitidis. Blastomyces dermatitidis oThree more species have been described: Blastomyces emzantsi, Blastomyces parvus and Blastomyces percursus. oAlong with two other important human-pathogenic fungi, Histoplasma capsulatum, Paracoccidioides brasiliensis and Polytolypa hystricis, species of Blastomyces belong to the family Ajellomycetaceae. oItself is a sexual organism, occurring in nature as both mating type and a non-mating type. Blastomyces dermatitidis oThis is epidemiologically important for two yet firstly, it implies that the organism will be genetically variable, potentially leading to variations in disease severity, treatment response and habitat preference, secondly, it implies that a suitable, stable habitat must exist for the complex process of sexual reproduction to take place. oThis habitat is as yet unknown. oIn its asexual form, the fungus grows as a typical colonial microfungus, comparable to Penicillium or Rhizopus mold forms commonly seen on mouldy bread. Blastomyces dermatitidis o In nature, the fungus forms a network of thread-like mycelium that penetrates the substratum on which it grows, and then after 3–5 days of growth begins to reproduce asexually with small 2–10 μm conidia. o They form on individual short stalks and readily become airborne when the colony is disturbed, their size places them well within the respirable size range for particles, meaning that they can deposit deeply in the lungs when inhaled. o Sexual reproduction by the Blastomyces dermatitidis requires the meeting of colonies of + and – mating type, probably a relatively rare event, and results in the production of small ascomata (sexual fruiting bodies) 200– 350 μm, looking, to the naked eye, similar to a woollen fuzz ball, and in microscopic view consisting of a layer of spiralling, springy guard hairs surrounding a fertile core in which groups of eight ascospores (sexual spores) are produced in small round reproductive sacs (asci). Blastomyces dermatitidis +The ascospores, at 1.5–2.0 μm, are among the smallest reproductive particles produced by fungi, and are within the respirable size range. Blastomycosis oA lung infection that is chronically invasive and spreads into the skin and bones, affecting both humans as well as animals. oA potentially very serious disease that typically begins with a characteristically subtle pneumonia-like infection that may progress, after 1–6 months, to a disseminated phase that causes lesions to form in capillary beds throughout the body, most notably the skin, internal organs, central nervous system and bone marrow. Coccidioides immitis o may cause an acute, benign, self-limiting respiratory infection or a chronic, malignant infection of the bones, joints, skin, lymph nodes, adrenal glands, and central nervous system. o The geographic distribution of the organism includes the southwestern United States and the semiarid areas of Mexico and Central and South America. o The infection has a high incidence in the San Joaquin Valley in California and may be commonly known as “desert fever” or “valley fever.” Coccidioides immitis o Large, thick-walled, round spherules that contain endospores are observed in direct preparations of tissue or body fluids. oAn extremely dangerous biohazard requiring Biosafety Level 3 containment. oIt may be considered the most infectious of all fungi. Coccidioides immitis +Along with its relative C. posadasii, is most commonly seen in the desert regions of the southwestern United States, including certain areas of Arizona, California, New Mexico, Nevada, Texas, and Utah; and in Central and South America in Argentina, Brazil, Colombia, Guatemala, Honduras, Mexico, Nicaragua, Paraguay, and Venezuela. Coccidioides posadasii oA pathogenic fungus that, along with Coccidioides immitis, is the causative agent of coccidioidomycosis, or valley fever in humans. oIt resides in the soil in certain parts of the Southwestern United States, northern Mexico, and some other areas in the Americas, but its evolution was connected to its animal hosts. Histoplasma capsulatum oIs found in the midwestern and southern United States and is endemic in the Mississippi and Ohio River Valleys and the Appalachian Mountains. Histoplasma capsulatum oCases also have been found in other areas of North America and in South America. oThe organism is saprobic in soil and multiplies in decaying chicken or pigeon droppings or bat guano. Histoplasma capsulatum o The primary infection involves the respiratory tract and may result in acute, chronic, or fatal pulmonary disease. o The chronic, cavitary form may resemble tuberculosis and is characterized by coughing and fever. o The infection may remain localized in the pulmonary tract but may disseminate also to the spleen, lymphatics, liver, kidneys, meninges, or heart. Histoplasma capsulatum oYeast cells are difficult to observe in direct sputum specimens. oHowever, small, round to oval yeast cells may be observed within monocytes or neutrophils on bone marrow or peripheral blood smears, using Wright’s or Giemsa stain. oA species of dimorphic fungus. Histoplasma capsulatum +Causes Histoplasmosis Paracoccidioides brasiliensis o causes a chronic granulomatous disease of the lungs, lymphatics, skin, and mucous membranes. o The organism is found most often in South and Central America and Mexico, especially in Brazil, Venezuela and Colombia. o It is rarely found in the United States. Paracoccidioides brasiliensis o Multiple budding yeast cells, which are said to resemble a “mariner’s wheel,” are observed on direct microscopic examination. oA dimorphic fungus and one of the two species that cause paracoccidioidomycosis, the other being Paracoccidioides lutzii. Penicillium marneffei ocauses systemic penicilliosis, an acute infection of the lungs, bone marrow, and other organs seen in immunocompromised hosts. Penicillium marneffei oThe infection has been found in Southeast Asia, China, India, and Hong Kong, and the organism has been isolated from the intestines of the bamboo rat. o Oval yeast cells that may resemble Histoplasma are observed within histiocytes on direct examination. Penicillium marneffei o The yeast cells elongate when observed outside of histiocytes. o P. marneffei grows as a Penicillium mold at 25°C as bluish green, powdery, velvety colonies. o Microscopically, the mycelial phase is observed as septate hyphae with brush-like conidiophores. Penicillium marneffei +Now known as the Talaromyces marneffei +It was identified in 1956. Cryptococcus neoformans o an encapsulated basidiomycetous yeastbelonging to the class Tremellomycetes and an obligate aerobe that can live in both plants and animals. o Its teleomorph is a filamentous fungus. o Formerly referred to Filobasidiella neoformans. Tests Reference/s: +Delost (All Edition) +Bailey and Scott’s (All Edition) +https://www.cancer.gov/publications/dictionaries/cancerterms/def/nucleus END
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