Non-O157 Shiga toxin-producing Escherichia coli: detection and characterization

Authors: Fratamico, Pina

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2009
Publication Date: 9/17/2009
Citation: Fratamico, P.M. 2009. Non-O157 Shiga toxin-producing Escherichia coli: detection and characterization. Meeting Abstract. p. 39-44.

Interpretive Summary:

Technical Abstract: Escherichia coli strains that produce Shiga toxins, referred to as Shiga toxin-producing E. coli (STEC) or verotoxigenic E. coli (VTEC) are important food-borne pathogens that cause hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). E. coli O157:H7 is a common cause of STEC infection; however, numerous non-O157 STEC strains belonging to serogroups O26, O103, O111, O145, and others have been associated with outbreaks and sporadic cases of HC and HUS worldwide. Cattle and other ruminants are important reservoirs for these pathogens, and various foods, particularly food of animal origin and water contaminated with animal feces have been associated with STEC infection. Detection of non-O157 STEC is problematic because these strains are indistinguishable from non-pathogenic E. coli employing conventional culture-based methods. Thus, little is known on the prevalence of non-O157 STEC in food, and the incidence of non-O157 STEC infection in the population is likely grossly underestimated. Methods for enrichment and isolation of STEC serogroups O26, O45, O103, O111, O121, and O145, the most common non-O157 STEC isolated from clinical cases in the U.S., have been developed, as well as detection methods based on the PCR targeting genes within the O-antigen gene cluster of different STEC serogroups and STEC virulence genes. In related studies, the DNA sequence of the large virulence plasmid of a STEC O26:H11 strain was determined. In addition to a large 168-kb virulence plasmid, the strain possessed 5 additional plasmids, and carried genes that conferred the ability to form biofilms. Additional research is needed to identify and characterize emerging non-O157 STEC serogroups, identify the animal reservoirs, and develop methods for detection of these pathogens, which will allow for control and surveillance of important STEC in food, animals, and the environment and an assessment of their importance in human infections.