Actinomycetes

BACK TO INFECTIOUS AGENTS AND PARASITES BACK TO BACTERIA

• 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 rod
    • Grows slowly on blood agar to produce small, white colonies surrounded by a zone of beta-haemolysis 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
  • 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
  • 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 sulphur granules
  • 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

• Actinbaculum suis in preputial mucosa of boars
• Actinobaculum have a coryneform morphology

Nocardia

• Aerobic short branching rods
• Cell wall contains mycolic acids (hence slightly acid fast)
• Nocardia asteroides found in soil
• Causes granulomatous lesions in animals
• Survives and multiplies in macrophages
• Chronic, progressive disease
• Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)