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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. 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
- Involved in deep pyoderma
Corynebacterium renale
- C. renale, C. pilosum, C. cystitidis
- Found in the vulva, vagina and prepuce of normal cattle
- Bovine pyelonephritis
- Stress of parturition and short urethra predisposes cows to urinary tract infection
- Cystitis especially with C. cystitidis
- Ascending infection from bladder through ureters causes pyelonephritis
- Fever, anoexia, decreased milk production
- Restlessness; kicking of abdomen indicate renal pain
- Dysurea, arched back, bloody urine
- Chronic infection causes extensive renal damage
- Enlarged ureters and kidneys palpated per rectum
- Culture from urine; protein and red blood cells in urine
- Antibiotics e.g. penicillin for at least three weeks
- Ulcerative balanoposthitis (pizzle rot):
- Common in Merino sheep and Angora goats
- Ulceration around prepucial orifice with brown crust, and occasionally on vulva of ewes
- Bacteria hydrolyse urea to ammonia which causes mucosal irritation and ulceration
- High urine urea level, from high protein intake may predispose to condition
- High oestrogen levels in pastures also predisposes
- Castration and heavy wool aroung the prepuce are risk factors
Corynebacterium bovis
- Subclinical mastitis in cattle
- Found in teat cistern
- Causes mild neutrophil response in teat canal of healthy dairy cows and may protect against invasion from more pathogenic bacteria
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