Genetic Diversity of Escherichia coli Isolated from Urban Rivers and Beach Water

Abstract

Repetitive element anchored PCR was used to evaluate the genetic profiles of Escherichia coli isolated from surface water contaminated with urban stormwater, sanitary sewage, and gull feces to determine if strains found in environmental samples reflect the strain composition of E. coli obtained from host sources. Overall, there was less diversity in isolates collected from river and beach sites than with isolates obtained from human and nonhuman sources. Unique strain types comprised 28.8, 29.2, and 15.0% of the isolate data sets recovered from stormwater, river water, and beach water, respectively. In contrast, 50.4% of gull isolates and 41.2% of sewage isolates were unique strain types. River water, which is expected to contain E. coli strains from many diffuse sources of nonpoint source pollution, contained strains most closely associated with other river water isolates that were collected at different sites or on different days. However, river sites impacted by sewage discharge had approximately 20% more strains similar to sewage isolates than did sites impacted by stormwater alone. Beach sites with known gull fecal contamination contained E. coli most similar to other beach isolates rather than gull isolates collected at these same sites, indicating underrepresentation of possible gull strains. These results suggest large numbers of strains are needed to represent contributing host sources within a geographical location. Additionally, environmental survival may influence the composition of strains that can be recovered from contaminated waters. Understanding the ecology of indicator bacteria is important when interpreting fecal pollution assessments and developing source detection methodology.

Escherichia coli in the Environment: Implications for Water Quality and Human Health

“…While more than 650 genotypes were observed among 1,535 unique E. coli strains based on repetitive element palindromic (rep)-PCR DNA fingerprinting, rarefaction analysis revealed that the diversity observed was not saturated 53) . Similar findings were also reported in other studies 3,66,69,119) . DNA fingerprint patterns are variable even within the same serotype.…”

Beach Sand and Sediments are Temporal Sinks and Sources of Escherichia coli in Lake Superior

“…The percentage of correctly classified strains in the DNA fingerprint library was analyzed by Jackknife analysis. Results in Table 1 show that E. coli strains in each source group were correctly classified >71% of the time, a relatively high rate of correct classification as compared to the previous reports (14,19). On average, 32% of the E. coli strains was identified to the source based on ID bootstrap analysis at P ) 0.90 ( Figure S2, Supporting Information).…”

“…The genetic relatedness of the E. coli isolates from the DBC beach to those in the libraries was determined by using ID bootstrap analysis (at P ) 0.90) as described (6). The percentage of correctly classified strains in each source group was analyzed by Jackknife analysis using maximum similarities (14,19).…”

Characterization of Escherichia coli populations from gulls, landfill trash, and wastewater using ribotyping

“…Others have used a 2-enzyme digest (Meays et al 2006), or separate ribotyping analyses with 2 different enzymes (Harwood et al 2003, Jenkins et al 2003, Jones et al 2006, to increase the potential diversity in ribopatterns. However, studies where DNA profiles from many isolates from an individual animal have been compared show saturations of diversity, or richness, at different numbers of profiles (Carson et al 2001, Johnson et al 2004, McLellan 2004, Anderson et al 2006. Myoda et al (2003) suggested DNA banding patterns produced by ribotyping and other genotypic methods are probably random with respect to what makes individual and hostspecific strains of target bacteria unique, so the added cost of using a second enzyme may not be necessary.…”