A Randomized Controlled Trial Assessing Infectious Disease Risks from Bathing in Fresh Recreational Waters in Relation to the Concentration of Escherichia coli , Intestinal Enterococci, Clostridium perfringens , and Somatic Coliphages

Abstract

We performed epidemiologic studies at public freshwater bathing sites in Germany to provide a better scientific basis for the definition of recreational water quality standards. A total of 2,196 participants were recruited from the local population and randomized into bathers and non-bathers. Bathers were exposed for 10 min and had to immerse their head at least three times. Water samples for microbiological analysis were collected at 20-min intervals. Unbiased concentration–response effects with no-observed-adverse-effect levels (NOAELs) were demonstrated for three different definitions of gastroenteritis and four fecal indicator organisms. Relative risks for bathing in waters with levels above NOAELs compared with nonbathing ranged from 1.8 (95% CI, 1.2–2.6) to 4.6 (95% CI, 2.1–10.1), depending on the definition of gastroenteritis. The effect of swallowing water provided additional evidence for true dose–response relationships. Based on the NOAELs, the following guide values for water quality are suggested: 100 Escherichia coli, 25 intestinal enterococci, 10 somatic coliphages, or 10 Clostridium perfringens per 100 mL. Recreational water quality standards are intended to protect the health of those consumers who are not already immune or resistant to pathogens that may be associated with indicator organisms. In contrast to current World Health Organization recommendations, we concluded that standards should be based on rates of compliance with NOAELs rather than on attributable risks determined above NOAELs, because these risks depend mainly on the unpredictable susceptibility of the cohorts. Although in theory there is no threshold in real concentration–response relationships, we demonstrated that a NOAEL approach would be a more robust and practical solution to the complex problem of setting standards.

Coliphages as Model Organisms in the Characterization and Management of Water Resources

“…Three of them only studied F-specific phages, and while Lee et al and Wade et al found some correlation [147,148], Van Asperen et al did not [149]. Wiedenmann et al only studied somatic coliphages and found some correlation [150]. In the studies where both phages were tested, the results are incongruent, since Von Schirnding et al failed to show any correlation with either somatic or F-specific phages [151], Colford et al found a correlation with F-specific phages [152], and Abdelzaher et al found a correlation with somatic coliphages [145].…”

Comparison of the presence and partitioning behavior of indicator organisms and Salmonella spp. in an urban watershed

“…Clostridium perfringens spores have been recommended as potentially more useful surrogates for protozoan pathogens such as Cryptosporidium and Giardia and for monitoring impacts of discharges on receiving waters (Medema et al 1997b;Lisle et al 2004;Wiedenmann et al 2006). In the present study, C. perfringens concentrations were determined using the multiple-tube fermentation method with iron milk medium as substrate (St John et al 1982;AOAC 1995).…”

“…Both types of coliphage have been recommended as surrogates for human enteric viruses (Havelaar et al 1993;Wiedenmann et al 2006). Samples for male-specific coliphage analysis were combined with tryptic soy agar supplemented with streptomycin-ampicillin and E. coli F amp as a host and poured into Petri dishes to solidify.…”

Abilities of the mCP Agar Method and CRENAME Alpha Toxin-Specific Real-Time PCR Assay To Detect Clostridium perfringens Spores in Drinking Water

“…According to Payment and Franco (3), Clostridium perfringens is a suitable indicator of human enteric viruses, Giardia cysts, and Cryptosporidium oocysts in finished water and can also be used in the assessment of water treatment processes due to the resistance of Clostridium spores to chlorine. Furthermore, the presence of C. perfringens in water is also associated with fecal contamination, and it has been evaluated and utilized as an alternative indicator of fecal pollution (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Thus, a simple and reliable culture-based method to isolate and enumerate C. perfringens, the membrane filtration method on mCP agar, has been elaborated and evaluated to monitor the presence of C. perfringens in water (15)(16)(17)(18)(19)(20).…”