Actinomycetes

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• Cause peritonitis in dogs and peritonitis in cattle and peritonitis in pigs

• Nocardia is involved in peritonitis and pleuritis in dogs

• Micropolyspora faeni and Thermactinomyces vulgaris in Bovine Farmers Lung

• Thermactinomyces vulgaris may cause COPD

• Actinomyces may cause granulomatous inflammation.
  • E.g. Actinomyces bovis -the cause of lumpy jaw and in osteomyelitis, may extend to surrounding muscles

• Actinomyces pyogenes in osteomyelitis

• In pyothorax

• Isolated from closed cases of Poll Evil and Fistulous Withers

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

Actinomyces, Arcanobacterium and Actinobaculum species

• Non-motile, non-spore-forming bacteria
• Anaerobic or facultative anaerobes
• Grow on enriched media; non-acid fast
• Colonise mucous membranes

• Arcanobacterium pyogenes
  • Characteristics:
    • Formerly known as Actinomyces pyogenes and Corynebacterium pyogenes
    • Small facultatively anaerobic rod
    • Grows slowly on blood agar to produce small, white colonies surrounded by a zone of beta-haemolysis after 48 hours
    • Produces hazy haemolysis after 24 hours; pin-point colonies after 48 hours
    • Coryneform morphology, like Chinese characters; may be curved with slightly swollen ends
    • Found in nasopharyngeal mucosa and genital tract of cattle, sheep, pigs
  • Pathogenicity
    • Opportunistic infections following injury or viral/mycoplasma infection in ruminants and pigs
    • Extracellular toxins including haemolysin, proteases, DNase and neurominidase
    • Haemolytic toxin, pyolysin, member of the thiol-activated cytolysins (pore-forming toxins); possibly cytotoxic to phagocytic cells; dermonecrotising activity
  • Clinical infections:
    • Suppurative infections
    • Abscesses especially in liver
    • Pyometra
    • Summer mastitis
    • Ovine foot disease
    • Umbilical infections
    • Pneumonia

• Actinomyces
• Usually long and filamentous branching Gram positive rods
• Anaerobic or facultativlyy anaerobic and capnophilic
• Live in nasopharyngeal and oral mucosa
• Cause pyogranulomatous lesions
  • Actinomyces bovis
    • Found naturally in oral cavity of cattle
    • Prefers anaerobic conditions but not strict anaerobe
    • Penetrates injured tissues to cause granulomatous lesions of soft tissues and bone, causing lumpy jaw
    • Organisms found in yellow sulphur granules
    • Club colony formation
    • Colonies adhere to agar media and are non-haemoltic
  • Actinomyces viscosus
    • Commensal of oral cavity of dogs and humans
    • Causes localised abscesses of skin or granulomatous lesions in thorax which may spread to abdomen causing pyothorax
    • Rods contained in soft grey granules which release the organism when squashed
    • Two types of colonies: large and smooth colonies with V, Y and T configurations or small and rough colonies with short branching filaments

• Actinobaculum suis
  • Found in preputial mucosa of boars
  • Anaerobic
  • Coryneform morphology
  • Produces urease
  • Produces lesions in urinary tract of sows
  • 3mm diameter colonies with shiny raised centre and dull edge

Nocardia

• Aerobic short branching rods
• Non-motile
• Spores from aerial filaments
• Grow on Sabouraud dextrose agar
• Cell wall contains mycolic acids (hence slightly acid fast)
• Nocardia asteroides found in soil
• Causes granulomatous lesions in animals
• Survives and multiplies in macrophages
• Lesions in thoracic cavity, skin and other tissues
• Chronic, progressive disease
• Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)

Dermatophilus congolensis

• Aerobic
• Motile zoospores
• No growth on Sabouraud dextrose agar
• Found in scabs and in foci on skin of carrier animals