Corynebacterium diphtheria is the most important member of the group, as it can produce a powerful exotoxin that causes diphtheria in humans. Corynebacterium species and related bacteria tend to be clubbed or irregularly shaped.
C diphtheria are 0.5-1 micromelimeter in diameter, bacilli irregular swelling at one end that give them club-shaped (clubbed end), stained with methyline blue dyes, grow well in blood agar colonies are small granular, and gray with irregular edges and small zones of hemolytic.
C. diphtheriae is pathogenic bacteria cause infection occurs in respiratory tract, in wound or on the skin. It is spread by droplets or by contact to susceptible individuals that grow on mucous membranes producing toxin as exotoxin which protein synthesis is responsible for the necroting and neurotoxic effects of diphtheria toxin. Diphtheria toxin is absorbed into the mucous membranes and causes destruction of epithelium and a superficial inflammatory response. The necrotic epithelium becomes embedded in exuding fibrin and red and white cells, so that a grayish " pseudomembrane " is formed—commonly over the tonsils, pharynx, or larynx. Any attempt to remove the pseudomembrane.
Sore throat and fever dyspnea soon follow because of the obstruction caused by the membrane damage to the heart.
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Swabs from the nose, throat, lesions also visible membrane the should be placed to media, On Loeffler's serum medium, Corynebacteria grow much more readily than other respiratory organisms, and the morphology of organisms is typical in smears.
Antimicrobial drugs as penicillin, erythromycin or new generation drugs inhibit the growth of diphtheria bacilli. Antitoxin is mandatory when there is strong clinical suspicion of diphtheria
Actinomycetes are aerobic, large group of gram-positive bacilli form chains or filaments include the important types Nocardia the most species case infections are:
Nocardia asteroids is caused Nocardiosis infection with Nocardia and related anaerobic or facultative bacteria. Pathogenic species:
- Actinomyces israelii
- Actinomyces naeslundii,
In most cases, Nocardiosis is an opportunistic infection associated with several risk factors, most of which impair the cell-mediated immune responses: corticosteroid treatment, immunosuppression, organ transplantation, AIDS, tuberculosis, and alcoholism. Nocardiosis begins as chronic lobar pneumonia, and a variety of symptoms may occur, including fever, weight loss, and chest pain.
These bacteria causes sub-acute to chronic pulmonary infection
Nocardia species are aerobic, gram +ve, Catalase +ve and partially acidfact bacilli, urease +ve. The bacteria bridge the mucosal or epithelial surface of the mouth, respiratory tract, or lower gastrointestinal tract—
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associated with dental caries, gingivitis, surgical complication, or trauma . Aspiration may lead to pulmonary infection.
.
Diagnostic lab.
By specimens of sputum, pus, spinal fluid and lotopsy material or gram-stained smears. Nocardia grow on most lab. Media.
Treatment:
of choice is trimethoprin or surgical drainage.
Bacillus anthracis the cause of anthrax is the most significant human pathogen. The characteristics of B. anthracis is gram positive rods, form spores oval, centrally located spores, non-motile, obligate aerobes, some facultative anaerobes. Capsulate and produce exotoxin. Infection by inhalation or rarely by ingestion which cause pulmonary anthrax or gastrointestinal anthrax bacteremia and secondary. Infection particularly meningitis. Usually infects an transmitted to human by infected animals and animal products which can be zoonosis. lab. Diagnosis :
Diagnosis of B. anthracis depends on a variety of biochemical properties, treatment is penicillin drugs choice.
Bordetella pertussis is the causative of whooping cough general properties of B. pertussis is nonmotile. gram-negative, short rod
(coccobacillus), capsulated, strict aerobe, non-spore forming, producing toxins pathogenesis of B. pertussis is a local pathogen of upper respiratory tract most of symptoms of whooping cough are directly related to mucosal by this organism lab.
Diagnosis by samples or swab (oral, nasal) cultured in media and isolate bacteria. Rapid diagnosis use smears of nasopharyngeal exudates are
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examined by direct immunofluorescence or by enzyme immunoassay
(EIA) or (ELISA). Erythromycin is the drug of choice.
The spirochetes are a large, heterogeneous group of spiral, motile bacteria. One family (Spirochaetaceae) of the order Spirochaetales consists of three genera of free-living, large spiral organisms. The other family (Treponemataceae) includes three genera whose members are human pathogens: (1) treponema, (2) borrelia, and (3) leptospira.
include two important of human pathogens Treponema and Borrelia. Treponema pallidum the etiologic agent of syphilis characteristic of T. pallidum long, thin, corkscrew-shaped 5-15
 m long with 6-14 coils. Microaerophilic, motile, not stain with gram. Use dark field examination. Endoflagella (axial filaments) are the flagella-like organelles in the periplasmic space encased by the outer membrane.
T. pallidum travels from site of infection (skin) to the lymph nodes then to blood stream, adheres to the cell, endothelial cell, endarteritis the lesion of syphilis cause inflammatory reaction and tissue necrosis to appear primary and secondary syphilis, latent stage followed congenital syphilis. Lab. Diagnosis use dark filed exam. And serological test as venereal disease research laboratory (VDRL) test.
penicillin is the choice. Other antibiotics, e.g., tetracyclines or erythromycin,
Characteristic
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The pseudomonads are gram-negative, motile, aerobic rods some of which produce water-soluble pigments. Pseudomonads occur widely in soil, water, plants, and animals. Pseudomonas aeruginosa is frequently present in small numbers in the normal intestinal flora and on the skin of humans and is the major pathogen of the group.
Pseudomonas aeruginosa is an obligate aerobe that grows readily on many types of culture media, Some strains hemolyze blood. P aeruginosa forms smooth round colonies with a fluorescent greenish color produce three types of pigment which diffuses into the agar : a.
Pyocyanin blue color-green color. b.
Fluorescent Pyroverdin green color-Dark brown. c.
Dark red pigment pyorubin or the black pigment
P aeruginosa have many virulence factors : capsule, Pili, flagella, protease, producing toxins Endotoxin and exotoxin cause diseases respiratory tract infections as outer and meddle ear infections, wounds, burn, UT/s and bacteremia. The bacterium attaches to and colonizes the mucous membranes or skin, invades locally, and produces systemic disease. These processes are promoted by the enzymes, and toxins described above. Lipopolysaccharide plays a direct role in causing fever, shock, oliguria, leukocytosis and leukopenia, disseminated intravascular coagulation, and adult respiratory distress syndrome.
Clinically significant infections with P aeruginosa should treated with penicillin active against P aeruginosa —combination with an aminoglycosides, tobramycin. quinolones, including ciprofloxacin. The newer cephalosporins, ceftazidime and cefoperazone are active against P aeruginosa .
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The most human pathogenic is Haemophilus influenzae which is gram-negative, short-rod (Coccobacilli). Non-motile, non-spore forming, facultative anaerobic non-capsulated (50-80%). Pathogenesis and disease cause meningitis, otitis media, sinusitis, pneumonia, bronchitis, conjunctivitis, arthritis, and bacteremia specialized capsulated.
This is a group of small, pleomorphic bacteria that require enriched media, usually containing blood or its derivatives, for isolation. H. influenzae type b is an important human pathogen; H ducreyi, a sexually transmitted pathogen, causes chancroid; other haemophilus species are among the normal flora of mucous membranes and only occasionally cause disease.
H influenzae is found on the mucous membranes of the upper respiratory tract in humans. It is an important cause of meningitis in children and occasionally causes respiratory tract infections in children and adults.
Treatment:
Ampicillin, Amoxicillin, third-generation Cephalosporin.
and
cause both diarrheal and systemic diseases and are among the most widespread causes of infection in the world.
Campylobacter jejuni are gram-negative rods with comma, S, or "gullwing" shapes. They are motile, with a single polar flagellum, and do not form spores.
C jejuni is susceptible to gastric acid, and ingestion of about
10 4 organisms is usually necessary to produce infection.
Helicobacter pylori is a spiral-shaped gram-negative rod it is associated with gastritis, duodenal (peptic) ulcer disease, gastric ulcers, and gastric carcinoma. Helicobacter pylori, which causes gastric infection. It has multiple flagella at one pole and is actively motile. H pylori is oxidase-positive and Catalasepositive, has a characteristic morphology, is motile, and is a strong producer of urease .
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