Escherichia coli

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• Enterotoxigenic E.coli contributes to undifferentiated neonatal calf diarrhoea, a mixed viral enteritis in calves.
• Colibacillosis.
• Histiocytic ulcerative colitis in the dog and cat.
• Causes secretory diarrhoea
• Causes peritonitis in dogs and peritonitis in pigs
• In osteomyelitis
• In neonatal polyarthritis of calves
• In arthritis of horses

Eschericia coli (E. coli) overview

• Member of Enterobacteriacae family of Gram-negative bacilli
• Facultative anaerobe
• One of predominant bacterial species in colonic flora
• Abundant in the environment
• Found in many non-specific, endogenous infections, eg. wound infections and upper respiratory tract infections and septicaemia
• Also and enteropathogen

E. coli characteristics

• Oxidase negative (do not possess cytochrome C oxidase)
• Grow on MacConkey agar (in presence of bile salts)
• Reduce nitrates to nitrits and ferment glucose to produce acid and gas
• Possess a lipolysaccharide (O) antigen, a flagellate (H) antigen, polysaccharide capsule (K) antigens and fimbrial (F) antigens
• Epidemiological typing of E. coli uses antigen combinations, eg. O125:K12:H42

Extra-intestinal infection

• Soft tissue infections in adult animals
• Most common organism infecting urinary tract
• Causes pyometra in the dog and cat and pyelonephritis
• Acute mastitis in lactating animals
• Pathogenesis:
  • Produces an alpha-haemolysin which may be cytotoxic
  • Iron aquisition system
  • K antigens prevent phagocytosis or mimic host antigens and resist complement
  • Fimbriae permit adhesion to mucosal surfaces
  • May enter blood to cause septicaemia
• Clinical infections:
  • Avian colibacillosis:
    • Septicaemia in newly-hatched chickens
    • Infection enters via faecal contamination of the egg surface or via the ovary of the hen
    • Infection enters via the respiratory tract
    • A bacteraemia develops
    • Acute colisepticaemia, subacute fibrinopurulent serositis or chronic granulomatous disease of the viscera
    • Occurs in older birds via inhalation of E. coli in dust; respiratory infection spreads to the blood to cause acute colisepticaemia
    • Airsacculitis, pericarditis and perihepatitis during acute phase
    • Often secondary to virus or mycoplamsa infection or environmental stress
  • Colisepticaemia:
    • Systemic disease in young calves, piglets, foals, lambs
    • Penetration of intestinal mucosa and entrance into the blood
    • Invasive strains survive the host defences
    • Virulence related to adhesive properties, complement resistance and ability for iron aquisition
    • Ammonia, dust, viral infections and temperature changes enhance likelihood of disease