- 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
- 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 in horses:
- 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