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Title: IMPACT OF MICROBIAL DIVERSITY ON RAPID DETECTION OF ENTEROHEMORRHAGIC ESCHERICHIA COLI IN SURFACE WATERS

Author
item Shelton, Daniel
item Karns, Jeffrey
item Higgins, James
item Van Kessel, Jo Ann
item Perdue, Michael
item BELT, KENNETH - USDA, FOREST SERVICE
item RUSSEL-ANELLI, JONATHAN - CORNELL UNIVERSITY, NY
item DEBROY, CHITRITA - PENNSYLVANIA STATE UNIV.

Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2006
Publication Date: 6/1/2006
Citation: Shelton, D.R., Karns, J.S., Higgins, J.A., Van Kessel, J.S., Perdue, M.L., Belt, K.T., Russel-Anelli, J., Debroy, C. 2006. Impact of microbial diversity on rapid detection of enterohemorrhagic Escherichia coli in surface waters. Federation of European Microbiological Societies Microbiology Letters. 261:95-101.

Interpretive Summary: Enterohemorrhagic Escherichia coli (EHEC) has emerged as a serious gastrointestinal pathogen in many countries. The symptoms of enterohemorrhagic E. coli infection include abdominal pain and bloody diarrhea, and in severe cases kidney failure that may result in death. Enterohemorrhagic E. coli was first reported in the U.S. in 1982 and has since been isolated from patients worldwide. Enterohemorrhagic E. coli infections, however, are not due to the global dissemination of a single virulent strain. Rather, they are a diverse collection of bacterial strains (including E. coli O157:H7) that appear to have evolved independently on several occasions. Although the predominant mode of transmission to humans is via consumption of contaminated meat and produce, outbreaks associated with water-borne strains have been documented worldwide. Consequently, rapid assays are needed that consistently detect water-borne enterohemorrhagic E. coli strains while excluding closely related non-enterohemorrhagic E. coli strains which do not pose a significant threat to human health. Recently, a variety of immunological and genetic methods have been developed for the rapid, sensitive detection of enterohemorrhagic E. coli that are potentially suitable for water analysis. However, the ability of these assays to reliably detect water-borne enterohemorrhagic E. coli has not been evaluated. We conducted a 30 month study (2002-2004) where water samples from the Baltimore, MD watershed (predominantly urban/suburban) were analyzed using an immunological assay for E. coli O157 (the predominant strain worldwide) and a genetic assay for two genes primarily responsible for pathogenicity. Although a substantial percentage of samples were positive for E. coli O157 cells or pathogenicity genes, few samples contained all three. Furthermore, the concentrations of O157 cells and genes in selected samples were rarely comparable. Several E. coli O157 strains were isolated from water samples; however, none were enterohemorrhagic E. coli. These data indicate that surface waters typically contain multiple strains similar to enterohemorrhagic E. coli, but less pathogenic, and that immunological or genetic assays cannot readily distinguish between them. Consequently, the inability of immunological and genetic assays to reliably identify water-borne enterohemorrhagic E. coli precludes rapid detection.

Technical Abstract: Enterohemorrhagic Escherichia coli are a physiologically, immunologically and genetically diverse collection of strains that pose a serious water-borne threat to human health. Consequently, rapid assays are needed that consistently detect water-borne enterohemorrhagic strains while excluding closely related non-enterohemorrhagic strains. Water samples from an urban/suburban watershed were analyzed using an immunological assay for E. coli O157 (the predominant strain worldwide) and a genetic assay for two genes responsible for pathogenicity. Although a substantial percentage of samples were positive for E. coli O157 cells or pathogenicity genes, few samples contained all three. Furthermore, the concentrations of O157 cells and genes in selected samples were rarely comparable. Several E. coli O157 strains were isolated, however, none were enterohemorrhagic. These data indicate the presence of multiple strains similar to enterohemorrhagic E. coli but less pathogenic. In conclusion, the inability of immunological and genetic assays to reliably identify water-borne enterohemorrhagic E. coli precludes rapid detection.