Difference between revisions of "Category:Actinomycetes"
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''[[Arcanobacterium pyogenes]]'' | ''[[Arcanobacterium pyogenes]]'' | ||
Revision as of 12:09, 10 May 2010
Overview
- Gram positive bacteria
- Grow slowly on media and produce branching filaments
- Opportunistic infections causing inflammatory responses and granulomatous reactions
- Animal pathogens include Actinomyces, Arcanobacterium, Actinobaculum, Nocardia and Dermatophilus
Arcanobacterium, Actinomyces and Actinobaculum species
- Non-motile, non-spore-forming bacteria
- Anaerobic or facultative anaerobes
- Grow on enriched media; non-acid fast
- Colonise mucous membranes
- Modified Ziehl-Neelson negative
<ncl style=bullet maxdepth=2 headings=bullet headstart=2 showcats=1 showarts=1>Category:Actinomycetes</ncl>
Arcanobacterium pyogenes
Actinobaculum suis
- Found in preputial mucosa of healthy boars
- Anaerobic
- Coryneform morphology
- Produces urease
- 3mm diameter colonies with shiny raised centre and dull edge
- Disease transmitted at coitus
- Sows develop disease within 3-4 weeks of mating
- Produces lesions in urinary tract of sows
- Cystitis and pyelonephritis in sows
- Anoreixa, arching of back, dysuria and haematuria
- May be fatal
Nocardia
- Facultative intracellular bacterium
- Aerobic short branching rods
- Non-motile
- Spores from aerial filaments when cultured
- Grow on Sabouraud dextrose agar
- Cell wall contains mycolic acids (hence slightly acid fast)
- Nocardia asteroides
- Found in soil and decaying vegetation - saprophytic
- Opportunistic infection of immunocompromised animals
- Infection via inhalation, wounds or teat canal; also ingestion
- Causes granulomatous lesions in animals
- Canine nocardiosis:
- Thoracic, cutaneous and disseminated forms
- Cutaneous pyogranulomas: ulcers or granulomatous swellings with discharging fistulae
- peritonitis
- pleuritis and pyothorax with fever, anorexia and respiratory distress
- Disseminated lesions
- Treat with appropriate systemic antibiotics for 6 weeks
- Cattle: chronic mastitis; abortion
- Pigs: abortion
- Sheep, goats, horses: wound infections; mastitis; pneumonia
- Survives and multiplies in macrophages
- Superoxide dismutase and catalase as well as a thick peptidoglycan wall prevent activity of phagocytes
- Chronic, progressive disease
- Positive modified Ziehl-Neelson
- Culture on blood agar and incubate under aerobic conditions at 37 degrees centigrade for 10 days
- White, powdery colonies, adherent to the agar appear after 5 days
- Subculture onto Sabouraud dextrose agar yields wrinkled, orange colonies
- Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)
- Cell-mediated immunity required
- Nocardia farcinica causes bovine farcy, a chronic infection of superficial lymphatic vessels and lymph nodes
Dermatophilus congolensis
- Filamentous, branching actinomycete
- Aerobic
- Produces motile zoospores
- No growth on Sabouraud dextrose agar
- Dermatophilosis most prevalent in tropical and subtropical regions
- Organisms found in scabs and in foci in skin of carrier animals
- Dormant zoospores become activated when moisture and temperature levels are favourable
- Zoospores may survive 3 years in scabs
- Pathogenicity:
- Does not usually invade healthy skin
- Entrance after trauma or persistent wetting
- Activated zoospores produce germ tubes which develop into filaments which invade the epidermis
- Invasion causes an accute inflammatory response with many neutrophils
- Microabscesses are formed in the skin
- Raised crusts develop in the affected regions
- Pathology
- Diagnosis:
- Giemsa-stained smears from scabs reveal branching filaments containing zoospores
- Immunofluorescence
- Scab material can be cultured on blood agar at 37 degrees centigrade, 2.5-10% carbon dioxide for 5 days
- Zoospores can be cultured
- After incubation, colonies are yellow and haemolytic (after 48 hours); they later become rough and yellow, and gain a mucoid appearance
- No growth on Sabouraud dectrose agar
- Clinical infections:
- Infection usually confined to epidermis
- Dermatophilosis
- Disease most prevalent in young animals
- Damage to the skin predisposes to infection; blood-sucking insects also thought to be involved in transmission
- Lesions after heavy rainfall predominantly affect dorsum of farm animals
- Papules, serous, exudative matting of hair, raised crusty scabs
- Scab formation more prominent in sheep and cattle than in horses
- Lesions may resolve within weeks if dry weather, or may progress
- Treatment:
- Parenteral antibiotics e.g oxytetracycline, pr penicillin-streptomycin combinations
- Micropolyspora faeni and Thermactinomyces vulgaris in Bovine Farmers Lung
- Thermactinomyces vulgaris may cause COPD
Subcategories
This category has the following 2 subcategories, out of 2 total.
Pages in category "Actinomycetes"
The following 5 pages are in this category, out of 5 total.