Category:Actinomycetes

From WikiVet English
Jump to navigation Jump to search

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=compact maxdepth=2 headings=bullet headstart=2 showcats=1 showarts=1>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


Subcategories

This category has the following 2 subcategories, out of 2 total.

A

N

Pages in category "Actinomycetes"

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