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With a growing interest in recreational water quality, there is a need for more affordable methods for detecting fecal indicator organisms, includingEscherichia coli(E. coli). Defined substrate technology (specifically Colilert) is a US Environmental Protection Agency approved method for the detection ofE. coliin beach water, but it requires relatively expensive equipment for enumeration of microbes. The 3M Petrifilm product is not currently approved for analysis of recreational water but has been approved for microbial analysis in the food industry. Both methods are simple to use, but Petrifilm requires less equipment and is less expensive than Colilert and thus has been used as a screening tool by citizens’ groups for enumeration ofE. coliin beach water. In some cases, however, the prescribed incubation at 35 C has been ignored. The objectives of this study were to compareE. coliconcentrations in beach water when enumerated by Colilert (defined substrate) and the PetrifilmE. colitest systems, and to evaluate the effects of incubation temperatures on Petrifilm results. Beach water collected from 20 beaches along lakes Michigan and Superior indicated that 19 beaches had meanE. coliconcentrations orders of magnitude higher when Petrifilm was compared to Colilert (4406 vs. 98 meanE.coli/100 mL). In most cases, use of Petrifilm would result in unnecessary advisories and closures at beaches. Incubation of Petrifilm at 25 or 30 C (below manufacturer's recommendation) required at least 2 days for colony counts to match concentrations enumerated by the recommended method. Overall, the Petrifilm method was not as reliable as currently accepted methods for measurement ofE. coliconcentrations in beach water. [ABSTRACT FROM PUBLISHER]

The seasonal variations and patterns of Escherichia coli in Wisconsin's coastal waters have been closely studied in recent years due to increased beach monitoring activities. Patterns of distribution of the indicator organism, E. coli, in the sand at these beaches are now being investigated as a source of E. coli to adjacent beach water. This project investigates the concentrations of E. coil in beach sand, and the relationship between these sand-microbe concentrations and concentrations of microbes in the corresponding beach water. Weekly sampling of upshore, swash, and submerged sand at six beaches provided numbers of the indicator bacteria in each beach's sand substrate for two consecutive summers. Overall concentrations of E. coil were highest in the swash sand of the beach, with the highest numbers seen in the summer months and lowest numbers in the winter months. Each location had very different concentrations of E. coli in the beach sand from 1,800 CFU/100 g to 21,670 CFU/100 g sand. Each location had a very different relationship between the indicator organism found in the beach sand and that found in the beach water. These data suggest that sand may be a reservoir for E. coii at some locations, and another source of contamination that should be considered in beach monitoring programs. However, elevated levels of E. coli in beach sand were not universal and varied greatly from location to location. [ABSTRACT FROM AUTHOR]

Abstract: While the US Environmental Protection Agency''s (EPA) Beaches Environmental Assessment and Coastal Health (BEACH) Act requires coastal and Great Lakes’ states to implement plans for monitoring bacterial contamination of recreational beach water, exactly how this monitoring should occur has not been regulated. This study examined differences in concentration of Escherichia coli in water collected from different depths and from different horizontal locations across the beach. E. coli concentrations were significantly different (p<0.05), when water from different depths was compared. Sampling water at depths of 30, 60, and 120cm resulted in significantly lower E. coli concentrations as depth increased. Had the State of Wisconsin chosen to collect beach water monitoring samples at a shallower or deeper depth, numbers of beach closures and the potential risk to public health would have changed substantially. These data imply that a revised and standardized protocol for monitoring beach water should be adopted by all states of a monitoring region to better compare microbial contamination of beaches and protect public health. [Copyright &y& Elsevier]

Abstract: High concentrations of Escherichia coli in mats of Cladophora in the Great Lakes have raised concern over the continued use of this bacterium as an indicator of microbial water quality. Determining the impacts of these environmentally abundant E. coli, however, necessitates a better understanding of their ecology. In this study, the population structure of 4285 Cladophora-borne E. coli isolates, obtained over multiple three day periods from Lake Michigan Cladophora mats in 2007–2009, was examined by using DNA fingerprint analyses. In contrast to previous studies that have been done using isolates from attached Cladophora obtained over large time scales and distances, the extensive sampling done here on free-floating mats over successive days at multiple sites provided a large dataset that allowed for a detailed examination of changes in population structure over a wide range of spatial and temporal scales. While Cladophora-borne E. coli populations were highly diverse and consisted of many unique isolates, multiple clonal groups were also present and accounted for approximately 33% of all isolates examined. Patterns in population structure were also evident. At the broadest scales, E. coli populations showed some temporal clustering when examined by year, but did not show good spatial distinction among sites. E. coli population structure also showed significant patterns at much finer temporal scales. Populations were distinct on an individual mat basis at a given site, and on individual days within a single mat. Results of these studies indicate that Cladophora-borne E. coli populations consist of a mixture of stable, and possibly naturalized, strains that persist during the life of the mat, and more unique, transient strains that can change over rapid time scales. It is clear that further study of microbial processes at fine spatial and temporal scales is needed, and that caution must be taken when interpolating short term microbial dynamics from results obtained from weekly or monthly samples. [Copyright &y& Elsevier]