Canis ISSN: 2398-2942

Escherichia coli

Synonym(s): E. coli

Contributor(s): Richard Walker

Introduction

Classification

Taxonomy

  • Family: Enterobacteriaceae.
  • Genus: Escherichia.
  • Species: coli.

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.
    • Enteroinvasive E. coli (EIEC): invade intestinal mucosa, release endotoxins, cause colisepticemia.
    • Enterohemorrhagic E. coli (EHEC): 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.
  • Greek: kolon - food, meat.

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Clinical Effects

Epidemiology

Habitat

  • Pathogenic and nonpathogenic strains of E. coli inhabit 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

  • Immunologic defense via:
    • Prevention of attachment to host cells.
    • Destruction of bacteria.
    • Neutralization of toxins.
  • Colostral antibodies important in protection against neonatal septicemia. Requires maternal exposure to the virulence determinants of the particular strain.

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 (<1 week old) because:
    • Normal flora not yet established.
    • Immature immune system.
    • Receptors for the adhesins of enterotoxigenic 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 of E. coli.
  • Recent change in feed and period of rapid growth, eg edema disease in pigs.
  • Surgery or contamination of wounds with fecal material.

Virulence factors of pathogenic E. coli strains

  • Capsular polysaccharide (K antigen).
  • Endotoxin (Lipid A) associated with septicemia and the toxemia in 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.)
  • Cytotoxic necrotizing factors.
  • 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 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 Cystitis.
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.
  • Coliform mastitis.
Poultry
  • Omphalitis.
  • Colisepticemia.
  • Coligranuloma (Hjarre's disease).
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. coli strains are sensitive to a wide range of antibiotics but resistance, often plasmid-mediated, is frequently encountered.
    Antimicrobial susceptibility pattern often unpredictable.
  • The use of antimicrobials Therapeutics: antimicrobial drug 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(8), 1168-75.
  • Hart C A et al (1990) Ultrastructural lesions to canine intestinal epithelium caused by enteropathogenic Escherichia coli. JSAP 31, 591.
  • Levine M (1987) Escherichia coli that cause diarrhea - enterotoxigenic, enteropathogenic, enteroinvasive, enterohemorrhagic and enteroadherent. J Infect Dis 155, 377.
  • Olson P et al (1985) Enterotoxigenic Escherichia coli (ETEC) and Klebisella pneumoniae isolated from dogs with diarrhea. Vet Microbiol 10, 577.

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