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United States Department of Agriculture

Agricultural Research Service


item Shelton, Daniel
item Karns, Jeffrey
item Higgins, James
item Van Kessel, Jo Ann
item Belt, Kenneth
item Debroy, C.

Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2006
Publication Date: 7/4/2006
Citation: Shelton, D.R., Karns, J.S., Higgins, J.A., Van Kessel, J.S., Belt, K.T., Debroy, C. 2006. Impact of microbial diversity on detection of water-borne enterohemorrhagic Escherichia coli [abstract]. 2nd FEMS Congress of European Microbiologists, July 4-8, 2006, Madrid, Spain.

Interpretive Summary:

Technical Abstract: Enterohemorrhagic Escherichia coli (EHEC) are a immunologically and genetically diverse collection of strains that pose a serious threat to human health. Immunological and PCR assays have been developed for the rapid, sensitive detection of presumptive EHEC. However, their ability to consistently detect EHEC while excluding non-EHEC strains has not been documented. We conducted a 30-month monitoring study of a major metropolitan watershed. Surface water samples were analyzed using an immunological assay for E. coli O157 and a multiplex PCR assay for the virulence genes stx1, stx2 and eae. The mean frequency of water samples positive for the presence of E. coli O157, stx1 or stx2 genes, or the eae gene was 50%, 26% and 96%, respectively. Quantitative analysis of selected enriched water samples indicated that even in samples containing E. coli O157 cells, stx1/stx2 genes, and the eae gene, the concentrations were rarely comparable. Seventeen E. coli O157 strains were isolated, however, none were EHEC. These data indicate the presence of multiple strains similar to EHEC. These findings have important ramifications for the detection of presumptive EHEC; namely, that current immunological or PCR assays cannot reliably identify water-borne EHEC strains.

Last Modified: 10/19/2017
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