Category:Actinomycetes
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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
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Arcanobacterium pyogenes
Actinobaculum suis
Nocardia
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.