Escherichia Coli, Diarrheagenic

Escherichia coli are gram-negative bacteria that inhabit the gastrointestinal tract. Most strains do not cause illness. Pathogenic E. coli are categorized into pathotypes on the basis of their virulence genes. Six pathotypes are associated with diarrhea (diarrheagenic): enterotoxigenic E. coli (ETEC), Shiga toxin–producing E. coli (STEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), and possibly diffusely adherent E. coli (DAEC). Other pathotypes that are common causes of urinary tract infections, bloodstream infections, and meningitis are not covered here. Serotypes of E. coli are determined by surface antigens (O and H), and specific serotypes tend to cluster within specific pathotypes. Some E. coli have virulence factors of more than 1 pathotype, and new strains of E. coli continue to be recognized as causes of foodborne disease. An example is the O104:H4 strain that caused an outbreak in Germany in 2011; it produced Shiga toxin and had adherence properties typical of EAEC.

STEC are also called verotoxigenic E. coli (VTEC), and the term enterohemorrhagic E. coli (EHEC) is commonly used to specify STEC strains capable of causing human illness, especially bloody diarrhea and hemolytic uremic syndrome (HUS).