Submitted to: Compendium of Methods for the Microbiological Examination of Foods
Publication Type: Book / chapter
Publication Acceptance Date: 5/30/2011
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Escherichia coli, a member of the Enterobacteriaceae family, is a part of the normal flora of the intestinal tract of humans and a variety of animals. E. coli strains are classified on the basis of antigenic differences in two surface components (serotyping), the somatic antigen (O) of the lipopolysaccharide and the flagellar (H) antigen. The O antigen identifies the serogroup of a strain, and the combination of O antigen and H antigen identifies its serotype. Although most E. coli are harmless commensals of the intestinal flora, certain groups are well known food-borne pathogens and can cause life-threatening diarrhea and severe sequelae or disabilities. Pathogenic E. coli are grouped based on virulence factors (virotype or pathotype), which include patterns of bacterial attachment to host cells, the production of various toxins, invasiveness, and other virulence-associated characteristics. Currently, pathogenic E. coli are categorized into six pathogenic groups: Enterotoxigenic E. coli, Enteroinvasive E. coli, Enterohemorrhagic E. coli, Enertopathogenic E. coli, Enteroaggregative E. coli, and Diffusely adherent E. coli. Since pathogenic E. coli are classified based on virulence factors, serotyping does not provide a definitive identification of the pathogenic group, as some strains with the same O type may belong to more than one pathogenic group. Additionally, the pathogenic E. coli groups are phenotypically diverse, so there are no specific methods to select and isolate each group; however, there are many rapid methods, including immunoassays and PCR-based assays that target specific virulence factors and genes, respectively, that can be used to screen food samples for the presence of the various pathogenic groups. Nevertheless, strain isolation from enrichments remains laborious and problematic since it is difficult to develop isolation media based on unique phenotypic differences among the E. coli groups. This chapter discusses the salient features and roles as food-borne pathogens of the different E. coli groups and current methods available for their detection from foods.