E. coli are Gram-negative, rod-shaped bacteria belonging to the family of
Enterobacteriaceae. Normally a useful organism in the human digestive system, but a few
E. coli strains are capable of causing human illness by several different mechanisms. The enterohemorrhagic
E. coli (EHEC) strain designated as
E. coli O157:H7 is the most important of the pathogenic
E. coli; it produces large quantities of one or more potent toxins that cause severe hemorrhagic colitis or hemolytic uremic syndrome. These toxins (verotoxin, shiga-like toxin) are closely related or identical to the toxin produced by
Shigella dysenteriae.
Five other pathogen mechanism types of
E coli are known:
- Enteropathogenic E. coli (EPEC): cause gastroenteritis (childhood diarrhea)
- Enteroinvasive E. coli (EIEC) or Shiga toxin-producing E. coli (STEC): cause a Shigella-like dysentery
- Εnterotoxigenic E coli (ETEC): cause traveler′s diarrhea
- Εnteroaggregative E coli (EaggEC): primarily associated with persistent diarrhea in children in developing countries
- Enteroadherent E coli (EAEC): cause childhood diarrhea and also traveler′s diarrhea
Most important EHEC serovares:
- O157
- O26
- O103
- O111
- O91
- O128
- O146
