Felis ISSN 2398-2950

Escherichia coli

Synonym(s): E. coli

Contributor(s): Richard Walker

Introduction

Classification

Taxonomy

  • Family: Enterobacteriaceae.
  • Genus: Escherichia.

Classification of enteritis-causing E. coli strains

  • Enterotoxigenic E. coli ( ETEC): have fimbrial adhesins, produce enterotoxin, cause neonatal colibacillosis.
  • Enteropathogenic E. coli (EPEC): do not produce enterotoxins or Shiga-like toxins, cause enteritis/diarrhea and colisepticemia by other mechanisms.
  • Attaching and effacing E. coli (AEEC): colonize small intestine, attach to target cells and kill them, Shiga-like toxins, isolated from calves and rabbits with enteric disease.

Etymology

  • Escherichia: named after Theodor Escherich, who named the type species of the genus.

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Clinical Effects

Epidemiology

Habitat

  • Pathogenic and non-pathogenic strains of E. coli inhibit the lower gastrointestinal tract.
  • Also abundant in the environment of animals.

Lifecycle

  • Reproduces by binary fission, usually in the gastrointestinal tract of the host.
  • Conjugation may occur with other bacteria to allow exchange of plasmids, which may bear toxin genes, and other transposable elements.

Transmission

  • Fecal oral route.

Pathological effects

Predisposers

  • Insufficient passive (colostral) immunity, ie neonates.
  • Poor environmental hygiene   →   build-up of pathogenic strain   →   may overcome normal levels of passive immunity.
  • Intensive farming methods   →   rapid transmission of pathogenic strains.
  • Age - (less than 1 week old) because:
    • Normal flora not yet established.
    • Immature immune system.
    • Receptors for the adhesins of E. coli only present for first week of life (calves) and first 6 weeks of life (piglets).
  • Stress factors, eg changed environment and diet in recently weaned pigs.
  • Heavy grain diets - allowing massive colonization of enterotoxigenic, K88 and K99 strains ofE. coli.
  • Recent change in feed and period of rapid growth, eg edema disease in pigs.

Virulence factors of pathogenic E. coli strains

  • Capsular polysaccharide (K antigen).
  • Endotoxin (Lipid A) associated with septicemia and the toxemia of coliform mastitis.
  • Certain fimbriae are protein adhesins.
  • Alpha and beta hemolysins.
  • Siderophores.
  • Heat-labile and heat-stable enterotoxins (LT enterotoxin is antigenically related to the cholera toxin).
  • Verotoxin or Shiga-like toxins - inhibit protein synthesis in host cells. Important in edema disease and in neonatal calves and piglets.

Opportunistic infections

  • E. coli strains, normally regarded as non-pathogenic can cause opportunistic infections, eg mastitis and metritis.

Other Host Effects

  • Predominant facultative species in large intestine.

Diseases associated with E. coli

Dog and cat
  • Neonatal colisepticemia.
  • Pyometra  Pyometra.
  • Urinary tract infection.

Pig

  • Neonatal diarrhea.
  • Colisepticemia.
  • Piglet meningitis.
  • Edema disease.
  • Coliform mastitis.
  • Mastitis-metritis-agalactia (MMA) syndrome.
Cattle
  • White scour.
  • Colisepticemia.
  • Joint ill.
  • Coliform mastitis.
Sheep
  • Colibacillosis and colisepticemia.
  • 'Watery mouth'.
  • Coliform mastitis.
Poultry
  • Omphalitis.
  • Colisepticemia.
  • Coligranuloma.
Other species
  • Colibacillosis and colisepticemia.

Control

Control via animal

  • Sound husbandry - the dam should be exposed to the local strains before parturition.
  • Some vaccines are available.
  • Maternal exposure to E. coli, either natural or artificial, allows for antibodies to be produced by the dam and secreted into the colostrum and milk.
  • Commercially produced preparations containing monoclonal antibodies to adhesins can be given orally to the neonate.

Control via chemotherapies

  • Most E. colis trains are sensitive to a wide range of antibiotics but resistance, often plasmid-mediated is frequently encountered.
  • The use of antimicrobials to treat the diarrhea is controversial.

Vaccination

  • Some are available.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Cullor J S (1995) Escherichia coli O157-H7 - the silent danger. Vet Med 90(1), 74-82.
  • Dorn C R (1995) Escherichia coli O157-H7. JAVMA 206(10), 1995.
  • Whipp S C, Rasmussen M A & Cray W C (1994) Animals as a source of Escherichia coli pathogenic for human beings. JAVMA 204(4), 1168-1175.
  • Levine M (1987) Escherichia coli that causes diarrhoea - enterotoxigenic, enteropathogenic, enteroinvasive, enterohaemorrhagic and anteroadherent. J Infect Dis155, 377.

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