Corynebacterium species

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• C. pyogenes in arthritis of sheep post-dipping joint infection and arthritis in pigs and arthritis in cattle

• Corynebacterium pseudotuberculosis may cause myositis
• Corynebacterium pseudotuberculosis in deep pyoderma

Overview

• Common inhabitants of skin and mucous membranes of animals
• Cause pyogenic infections
• Most species host specific

Characteristics

• Small, tough, Gram positive rods
• Pleomorphic
• Cluster together to resemble Chinese characters - coryneform morphology
• Known as diphtheroids
• Catalase positive, oxidase negative
• Facultative anaerobes
• Require enriched media for growth
• Non-motile

Clinical infections

• Infection follows tissue trauma
• Suppurative lesions
• C. pseudotuberculosis casues caseous lymphadenitis in sheep
• Carried on skin of sheep
• Produces a phospholipase toxin
• Infection through shearing wounds
• Facultative intracellular pathogen inside macrophages
• Ulcerative lymphangitis in horses

Diagnosis

• Colony characteristics@
  • C. bovis: lipophilic bacterium; small, white, dry, non-haemolytic colonies on plates inoculated with bovine milk
  • C. kutscheri: white colonies; occasionally haemolytic
  • C. pseudotuberculosis: small, white coloniess surrounded by narrow zone of complete haemolysis; colonies become dry and cream-coloured
  • C. renale: small, non-haemolytic colonies after 24 hours; pigment produced after 48 hours
• Biochemical reactions:
  • Certain strains of C. pseudotuberculosis reduce nitrates
  • All pathogenic strains except C. bovis produce urease
• Enhancement of haemolysis produced by C. pseudotuberculosis when inoculated across a streak of Rhodococcus equi