Corynebacterium species

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

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 suppurative infections except for C. bovis
• C. bovis causes mild neutrophil response in teat canal of healthy dairy cows and may protect from more pathogenic bacteria
• C. pseudotuberculosis:
  • Facultative intracellular pathogen inside macrophages
  • Cell wall lipid
  • Produces a phospholipase toxin which hydolyses sphingomyelin in mammalian cell membranes
  • Phospholipase may enhance survival and multiplication in host in early stages
• C. renale
  • Urinary tract pathogens
  • Produce urease and hydrolyse urea
  • Possess fimbriae for attachment to urogenital mucosa
  • Infection when immunity reduced or following tissue damage during parturition

Corynebacterium pseudotuberculosis

• Caseous lymphadenitis:
  • C. pseudotuberculosis carried on skin of sheep
  • Non-nitrate-reducing biotype
  • Infection follows tissue trauma such as shearing wounds
  • Incubation period 3 months
  • Chronic suppurative infection of sheep, goats and occasionally cattle
  • Abscessation of superficial and internal lymph nodes if haemtogenous spread occurs
  • Caseous abscesses with green colour and onion ring appearance
  • Ill thrift and pneumonia may occur
  • Condemnation of carcasses and hides
  • Infection spread by pus from abscesses, and oculonasal secretions
  • Organism survives in environment for several months
  • Sandwich ELISA detects circulating antibodies to phospholipase toxin
  • Control: importation measures including screening; culling of infected sheep, stict hygiene; inactivated vaccine
• Ulcerative lymphangitis:
  • Nitrate reducing biotype
  • Disease in horses and cattle
  • Infection through skin wounds
  • Lymphangitis of lower limbs or abscessation in pectoral region
  • Slow onset, usually becomes chronic
  • Affected lymphatic vessels swollen and firm with nodules
  • Oedema in affected limbs
  • Ulcerative nodules exude thick green pus
  • Lymphangitis and lymphadenitis in cattle with abscesses as well as coronary band lesions causing lameness
  • Antibiotic treatment and topical iodophore shampoo
• May cause myositis
• In deep pyoderma

Diagnosis

• Samples include pus, exudate, affected tissues and urine
• Presence of coryneform organisms in smears
• Culture on blood agar, selective blood agar and MacConkey agar
• Do not grow on MacConkey
• 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