Foodborne Illness Caused by Escherichia coli: A Review

Abstract

Enteropathogenic Escherichia coli (EEC) can be defined as any strain of E. coli that has the potential to cause diarrheal illness. Four major categories of EEC exist. Classical enteropathogenic E. coli (EPEC) commonly refers to serogroups of E. coli historically associated with outbreaks of diarrhea in young children and infants. Facultatively enteropathogenic E. coli (FEEC) are non-EPEC serogroups associated with sporadic diarrhea, and include many serogroups associated with the normal intestinal flora. Enterotoxigenic E. coli (ETEC) is commonly isolated from outbreaks of traveler's diarrhea, and includes those strains which produce a heat-stable enterotoxin (ST) only, a heat-labile enterotoxin (LT) only and those which produce both ST and LT. These organisms adhere to and colonize the epithelial cell surfaces of the proximal small intestine. This colonization is mediated by specific types of fimbriae which are host-specific. Toxigenicity is plasmid-related. Enteroinvasive E. coli (EIEC) exert their pathogenic effect through an invasive infection of the gastrointestinal tract. Many techniques currently exist to determine the presence of enterotoxins produced by a particular strain of E. coli. These include bioassay, tissue culture and in vitro immunological techniques. Of the newer in vitro immunological methods, the staphylococcal coagglutination technique to detect LT seems to have potential for routine use in diagnostic microbiology laboratories. Since large numbers (106 – 109) of EEC are necessary for diarrhea, an unsanitary environment is needed for transmission of illness. Presence of EEC varies geographically; however, E. coli diarrhea is not likely to occur in the more hygenic areas of the world, except in occasional common-source outbreaks where the organism has time to replicate in food or water. The following foods have been implicated in documented E. coli diarrheal outbreaks worldwide: meat and meat products, fish, poultry, milk and dairy products, vegetables, baked products, rice formulations, coffee substitutes and water.