F-specific coliphages and their serogroups, and Bacteroides fragilis phages as indicators of estuarine water and shellfish quality

Fecal contamination of coastal areas used for primary contact recreation and harvesting of bivalve molluscan shellfish is a health concern. The bacterial indicators used to judge the sanitary quality do not reliably predict viral contamination or risk from them. F-specific (F+) RNA coliphages and Bacteroides fragilis (BF) phages have been suggested as indicators for viral contamination in water, but systematic studies are limited in seawater and shellfish. In this study, we performed a comprehensive investigation on these phages as indicators, which included (i) development of detection methods, (ii) virus survival experiments, and (iii) field studies in a well-characterized estuarine creek subject to human, point source sewage effluent contamination. In field studies, bacterial indicators, including fecal coliforms, E. coli, enterococci, and Cl. perfringens were analyzed in water and oysters, and enteric viruses were analyzed in oysters by cell culture followed by RT-PCR and oligoprobing for enhanced detection.;F+ coliphages on hosts S. typhimurium WG49 and E. coli Famp were enumerated with adequate recovery from seawater using membrane filter methods, and from oysters by extraction in nutrient broth. They were conservative predictors of sewage treatment efficacy (primary and secondary treatment and chlorination) and of fecal contamination in oysters and receiving waters. Furthermore, their levels were associated with the degree of fecal contamination. However, their greater inactivation then enteric viruses in seawater at high temperature compromises the usefulness of F+ coliphages as indicators of viral contamination. The usage of F+ coliphage serotyping was generally successful in distinguishing between human and animal fecal contamination. The exception was for pigs. F+ coliphage serogroup II, which is predominant in human sewage in this region, also was abundant in pig feces and swine lagoon waste.;BF phages on B. fragilis VPI 3625 showed greater survival in seawater then the enteric viruses tested. However, they were unsuitable as indicators because (i) the levels in treated sewage effluent and receiving water and oysters were too low for reliable detection, and (ii) the recoveries of detection methods were not as reliable as for coliphages due to small plaque size. BF phages detected on host VPI 3625 were not specific indicators of human fecal contamination.