Difference between revisions of "Category:Actinomycetes"

Revision as of 12:11, 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=0>Category:Actinomycetes</ncl> Arcanobacterium pyogenes

Actinomyces

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.

A

► Actinomyces‎ (3 P)

N

► Nocardia species‎ (2 P)

Pages in category "Actinomycetes"

The following 5 pages are in this category, out of 5 total.

A

D

Dermatophilus congolensis

R

Renibacterium salmoninarum

@@ Line 15: / Line 15: @@
-<big>'''''<ncl style=compact maxdepth=2 headings=bullet headstart=2 showcats=1 showarts=1>Category:{{PAGENAME}}</ncl></big>
+<big>'''''<ncl style=bullet maxdepth=2 headings=bullet headstart=2 showcats=1 showarts=0>Category:{{PAGENAME}}</ncl></big>
 ''[[Arcanobacterium pyogenes]]''
@@ Line 23: / Line 23: @@
 ===''[[Actinobaculum suis]]''===
-===''Nocardia''===
+===''[[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, [[Bacterial skin infections - Pathology#bacterial granulomatous dermatitis|cutaneous]] and disseminated forms
-***Cutaneous pyogranulomas: ulcers or granulomatous swellings with discharging fistulae
-***[[Peritoneal Cavity Inflammatory - Pathology#In dogs|peritonitis]]
-***[[Respiratory Bacterial Infections - Pathology#Nocardiosis|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