Gene and Antigen Markers of Shiga‐toxin Producing E. coli from Michigan and Indiana River Water: Occurrence and Relation to Recreational Water Quality Criteria

Abstract

The relation of bacterial pathogen occurrence to fecal indicator bacteria (FIB) concentrations used for recreational water quality criteria (RWQC) is poorly understood. This study determined the occurrence of Shiga-toxin producing Escherichia coli (STEC) markers and their relation to FIB concentrations in Michigan and Indiana river water. Using 67 fecal coliform (FC) bacteria cultures from 41 river sites in multiple watersheds, we evaluated the occurrence of five STEC markers: the Escherichia coli (EC) O157 antigen and gene, and the STEC virulence genes eaeA, stx1, and stx2. Simple isolations from selected FC cultures yielded viable EC O157. By both antigen and gene assays, EC O157 was detected in a greater proportion of samples exceeding rather than meeting FC RWQC (P < 0.05), but was unrelated to EC and enterococci RWQC. The occurrence of all other STEC markers was unrelated to any FIB RWQC. The eaeA, stx2, and stx1 genes were found in 93.3, 13.3, and in 46.7% of samples meeting FC RWQC and in 91.7, 0.0, and 37.5% of samples meeting the EC RWQC. Although not statistically significant, the percentage of samples positive for each STEC marker except stx1 was lower in samples that met, as opposed to exceeded, FIB RWQC. Viable STEC were common members of the FC communities in river water throughout southern Michigan and northern Indiana, regardless of FIB RWQC. Our study indicates that further information on the occurrence of pathogens in recreational waters, and research on alternative indicators of their occurrence, may help inform water-resource management and public health decision-making.

Escherichia coliO157:H7: Animal Reservoir and Sources of Human Infection

“…Nontoxigenic bacteria are used as indicators of pathogen contamination potential, but migration potential of toxigenic and nontoxigenic strains may differ (Castro and Tufenkji, 2007). The presence of EC O157 in local recreational water was not related to fecal indicator bacteria (Duris et al, 2009), but the presence of bovine-specific species of Bacteroidales was a good predictor for contamination by EC O157 (Walters et al, 2007), although EC O157:H7 were rarely detected in the absence of indicator E. coli within a large geographic setting, such as a river basin in Canada (Wilkes et al, 2009). Interestingly, EC O157:H7 do not survive well in the Ganges river water due to heat-labile noncellular antimicrobials, presumably colicins or antimicrobial peptides (Nautiyal, 2009).…”

Predictive Models for Escherichia coli Concentrations at Inland Lake Beaches and Relationship of Model Variables to Pathogen Detection

“…While ruminant species, such as cows and deer, are the primary reservoir of pathogenic E. coli, these pathogens have also been found in humans, swine, and other domestic and wild animals as host organisms (12). Markers of pathogenic E. coli have been found in river systems that can influence beach environments (13). Salmonella species are recognized for having a very large host range that includes humans, birds, and most other warm-blooded animals (14), but gulls and sewage are recognized as important sources of Salmonella in recreational waters (15).…”

“…Salmonella enterica was identified using methods adapted from the work of Chiu and Ou (24) to detect the invasion A (invA) and Salmonella plasmid of virulence (spvC) genes. Pathogenic Shiga-toxin producing E. coli (STEC) was identified by following the methods of Duris et al (13) to detect the Shiga toxin 1 and 2 genes (stx 1 and stx 2 ), the intimin (eaeA) gene, and a generic 16S rRNA gene marker for E. coli in a four-gene multiplex PCR. E. coli O157 was detected using the methods of Osek (25) to detect the gene encoding the O157 surface protein (rfb O157 ).…”

Evaluating the Pathogenic Potential of Environmental Escherichia coli by Using the Caenorhabditis elegans Infection Model

“…In this context, specific virotypes can tentatively be ascribed to environmental isolates on the basis of virulence gene profiling, the assumption being that specific complements of virulence genes are associated with the ability to cause specific diseases (6)(7)(8). The virulence gene profiling approach has been used to characterize the seasonal and spatial distribution of waterborne E. coli that are potentially pathogenic to humans or livestock and to identify associations in virotype distribution within catchments with variation in land use, climate, and the distribution of potential sources of fecal contamination (9)(10)(11)(12)(13)(14)(15). There are, however, practical problems with the tractability of the virulence gene profiling approach.…”