Abstract
Rapid molecular testing methods and alternative FIBs such as the Bacteroidales group have been advocated to supplement or replace the current water quality testing methods and indicators. The objectives of this study were to evaluate risk to humans from exposure to subtropical recreational marine waters with no known point source, and investigate the possible relationships between traditional and alternative FIBs as measured by culture-based and molecular-based methods vs reported symptoms in human subjects with random exposure assignments and intensive individual microbial testing of their personal space water exposures. Staphylococcus aureus and other pathogens were also tested for and compared against reported symptoms. Over a period of seven months, 1303 adult regular bathers were randomly assigned to bather or non-bather groups, with subsequent follow-up for reported illness. Extensive environmental sampling and measurement of traditional and alternative indicator organisms (enterococci and Bacteroidales group) by culture and by quantitative PCR followed, along with several assays for selected pathogens. An increase of self-reported illness among bathers vs. non-bathers was observed, and dose response relationships by logistic regression modeling also observed for enterococci enumeration by membrane filtration vs. skin illness, for enterococci enumeration by qPCR vs. acute febrile respiratory illness, and for Human-specific Bacteroides enumerated by qPCR vs. skin illness and gastrointestinal illness The observed odds risk ratios and dose response curves for these alternative indicators and methods vs. reported health affects are suggestive. However, examination of the area under the ROC curve for these logistic regression models of FIBs vs. illness demonstrated only a borderline significant discrimination power only for the Enterococci membrane filtration enumeration vs. skin ailments. In addition methicillin-resistant S. aureus was observed. However, no correlation was observed between levels of Staphylococcus and any self-reported symptoms or illness. A variety of environmental parameters were also analyzed by multiple logistic regression models, but only one demonstrated a clear dose response (an inverse relationship between water temperature and respiratory illness). It may be that the sample size of this study was not large enough to elucidate a clearer relationship between specific FIB markers or pathogens and specific illnesses. Still, this study indicates that bathers may be at increased risk of illness relative to non-bathers, even in the absence of any known source of sewage impacting the recreational marine waters.