Corynebacterium species

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

Overview

  • Common inhabitants of skin and mucous membranes of animals
  • Opportunistic infections
  • 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


Pathogenesis and pathogenicity

  • Pyogenic causing


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