Ecoli Properties

Gram negative rod,Facultative anaerobic,motile,Oxidase negative

Antigens:Somatic antigen O,capsular antigen K,Flagellar antigen H.


Divided into 5 types.

1.Enteropathogenic Ecoli(EPEC)

  1. Non Invasive
  2. Adheres tightly to enterocytes using intimin leading to loss of microvilli.
  3. Causes infantile diarrhoea.

2.Enterotoxigenic Ecoli(ETEC)

  1. Noninvasive
  2. Most important cause of travelers diarrhoea.


  • Heat labile Cholera like enterotoxin(LT) acts by stimulating cAMP.
  • Heat stable toxin(ST) acts by cGMP,causes a disease resembing cholera in infants(Cholera infantum)

3.Enterohemorrhagic Ecoli(EHEC)

  1. Moderately invasive
  2. Produces cytotoxin called verotoxin resembling shiga toxin.
  3. EHEC 0517:H7 causes HUS.

4.Enteroinvasive Ecoli(EIEC)

  1. Invasive,penetrate and multiply inside epithelial cells.
  2. Does not produce enterotoxins
  3. Sereny test:EIEC in eyes of guinea pigs cause keratoconjunctivitis
  4. Invasion of HeLa cells in tissue culture used for diagnosis.
  5. Produce dysentry clinically resembling Shigellosis

5.Enteroaggregative Ecoli(EAEC)

Cause travelers diarrhoea, acute and persistant diarrhoea.

Uropathogenic Ecoli

UPEC use P fimbriae(pyelonephritis associated fimbriae) to bind to urinary tract endothelial cells.

Cause 90% UTI in anatomically normal urinary tracts.

E.coli with Kappa antigens most commonly responsible for upper UTI(pyelonephritis),while most isolates from cystitis lack Kappa antigens.

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