Impact of microbial diversity on rapid detection of enterohemorrhagic Escherichia coli in surface waters

• Published in: FEMS microbiology letters 2006-08, Vol.261 (1), p.95-101
• Main Authors: Shelton, Daniel R, Karns, Jeffrey S, Higgins, James A, Van Kessel, Jo Ann S, Perdue, Michael L, Belt, Kenneth T, Russell-Anelli, Jonathan, DebRoy, Chitrita
• Format: Article
• Language: English
• Subjects: Adhesins, Bacterial - genetics; Assaying; Bacteria; bacterial contamination; Bacteriological methods and techniques used in bacteriology; Bacteriology; Biological and medical sciences; E coli; eae gene; enterohemorrhagic Escherichia coli; enteropathogenic Escherichia coli; Escherichia coli; Escherichia coli O157 - classification; Escherichia coli O157 - genetics; Escherichia coli O157 - isolation & purification; Escherichia coli O157:H7; Escherichia coli Proteins - genetics; Fundamental and applied biological sciences. Psychology; Genes; Immunoassay - methods; immunoassays; Immunology; immunomagnetic electrochemiluminescence; Microbiology; Microorganisms; pathogen identification; polymerase chain reaction; Polymerase Chain Reaction - methods; Serotyping - methods; Shiga Toxin 1 - genetics; Shiga Toxin 2 - genetics; strains; Surface water; verotoxigenic Escherichia coli; Virulence; Water analysis; Water Microbiology; water pollution; Water sampling; water‐borne Escherichia coli
• ISSN: 1574-6968; 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.2006.00334.x

Enterohemorrhagic Escherichia coli (EHEC) are a physiologically, immunologically and genetically diverse collection of strains that pose a serious water-borne threat to human health. Consequently, immunological and PCR assays have been developed for the rapid, sensitive detection of presumptive EHEC. However, the ability of these assays to consistently detect presumptive EHEC while excluding closely related 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 (the predominant strain worldwide) 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 positive for 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 but less pathogenic. These findings have important ramifications for the rapid detection of presumptive EHEC; namely, that current immunological or PCR assays cannot reliably identify water-borne EHEC strains.