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Beach Sand Analysis for Indicators of Microbial Contamination
Prevette, E. B., C. D. Heaney, T. J. WADE, E. A. SAMS, AND J. R. Stewart. Beach Sand Analysis for Indicators of Microbial Contamination. Presented at Water and Health: Where Science Meets Policy Conference, Chapel Hill, NC, October 24, 2010.
This study explored the use of alternative indicators in beach sand and also evaluated a rapid technique for the detection of coliphages.
Traditional beach monitoring has focused on water quality, with little attention paid to health risks associated with beach sand. Recent research has reported that fecal indicator bacteria, as well as human pathogens can be found in beach sand and may constitute a risk to human health. This study explored the use of alternative indicators in beach sand and also evaluated a rapid technique for the detection of coliphages. Indicators evaluated included male-specific and somatic coliphages as viral indicators of fecal contamination, along with Staphylococcus aureus, a potential opportunistic pathogen. Sand was collected from two beaches during the summer of 2009. Study sites included Boqueron Beach in Puerto Rico, a representative subtropical beach; and Surfside Beach in South Carolina, a representative beach impacted by non-point source pollution. Laboratory analysis of the sand for viral indicators yielded compelling results: Coliphages were detected in 25 of 81 samples (30.8%) from Boqueron Beach, and in 83 of 87 samples (95.4%) from Surfside Beach. Somatic coliphages were detected more frequently than male-specific coliphages, with 60.1% and 29.0% of samples testing positive, respectively. The rapid 5 hour detection technique appears better suited to detection of somatic coliphages than male-specific coliphages. Somatic coliphages were detected in 52.4% of samples after a 5 hour enrichment and in 56% of samples after 24 hours. Male-specific coliphages were only detected in 14.9% of samples after a 5 hour enrichment, with 28.0% of samples positive after 24 hours. Out of 156 sand samples analyzed for S. aureus using selective media, 116 (74.4%) were positive for growth with colony morphologies characteristic of S. aureus. Presumptive S. aureus strains were archived, along with strains showing variable colony morphologies, for further characterization. These isolates will be analyzed to confirm species identity and screened to detect the possible presence of methicillin-resistant S. aureus (IVIRSA). Overall, this study will help identify appropriate measures to evaluate public health risks associated with beach sand, which may include the use of alternative indicators. This is an abstract of a proposed presentation and does not represent EPA policy