Escherichia coli enterohemorrhagic (EHEC): Dose Response Models

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Overview: EHEC and disease caused by it

Escherichia coli usually exists as a commensal bacterium in the mammalian large intestine, benefiting itself as well as the host. Enterohemorrhagic E. coli (EHEC; particularly serotype O157:H7) is a highly pathogenic variant which can cause life-threatening disease and has been the cause of many major outbreaks from fecally contaminated food (e.g., ground beef)[1] It may be spread by contaminated drinking water as well; for example, a large outbreak occurred in Walkerton, Ontario following heavy rains[2]

EHEC is technically part of the larger group of Shiga toxin producing E. coli (STEC), many of which cause little or no disease. EHEC attaches to the large intestinal wall and produces ‘attaching and effacing lesions’. It can cause bloody or non-bloody diarrhea, as well hemorrhagic colitis and hemolytic uremic syndrome (HUS). Its principal reservoir is the bovine intestinal tract. It has a lower ID50 than other pathogenic E. coli types [3][4]

It is unethical to conduct feeding experiments on humans with EHEC due to its virulence. However, feeding experiments on animals have been conducted. Information from EHEC outbreaks in humans has also been used to inform dose response models.


  1. Strachan NJC et al. (2005) Dose response modelling of Escherichia coli O157 incorporating data from foodborne and environmental outbreaks. International Journal of Food Microbiology. 103(1), pp.35-47. Full Text
  2. Auld H, MacIver D & Klaassen J (2004) Heavy rainfall and waterborne disease outbreaks: the Walkerton example. Journal of Toxicology and Environmental Health. Part A. 67(20-22), pp.1879-1887. Full Text
  3. Kaper JB, Nataro JP & Mobley HL (2004) Pathogenic Escherichia coli. Nature Reviews. Microbiology. 2(2), pp.123-140. Full Text
  4. Nataro JP & Kaper JB (1998) Diarrheagenic Escherichia coli. Clinical Microbiology Reviews. 11(1), pp.142-201. Full Text