Clifford C. Rankin

Rapidly measured indicators of recreational water quality and swimming-associated illness at marine beaches: a prospective cohort study.

IntroductionIn the United States and elsewhere, recreational water quality is monitored for fecal indicator bacteria to help prevent swimming-associated illnesses. Standard methods to measure these bacteria take at least 24 hours to obtain results. Molecular approaches such as quantitative polymerase chain reaction (qPCR) can estimate these bacteria faster, in under 3 hours. Previously, we demonstrated that measurements of the fecal indicator bacteria Enterococcus using qPCR were associated with gastrointestinal (GI) illness among swimmers at freshwater beaches. In this paper, we report on results from three marine beach sites.MethodsWe interviewed beach-goers and collected water samples at marine beaches affected by treated sewage discharges in Mississippi in 2005, and Rhode Island and Alabama in 2007. Ten to twelve days later, we obtained information about gastrointestinal, respiratory, eye, ear and skin symptoms by telephone. We tested water samples for fecal indicator organisms using qPCR and other methods.ResultsWe enrolled 6,350 beach-goers. The occurrence of GI illness among swimmers was associated with a log10-increase in exposure to qPCR-determined estimates of fecal indicator organisms in the genus Enterococcus (AOR = 2.6, 95% CI 1.3-5.1) and order Bacteroidales (AOR = 1.9, 95% CI 1.3-2.9). Estimates of organisms related to Clostridium perfringens and a subgroup of organisms in the genus Bacteroides were also determined by qPCR in 2007, as was F+ coliphage, but relationships between these indicators and illness were not statistically significant.ConclusionsThis study provides the first evidence of a relationship between gastrointestinal illness and estimates of fecal indicator organisms determined by qPCR at marine beaches.

Interlaboratory evaluation of MI agar and the US Environmental Protection Agency-Approved Membrane Filter Method for the recovery of total coliforms and Escherichia coli from drinking water☆

Abstract A new membrane filter (MF) medium, MI agar, recently validated for use in recovering chlorine-damaged total coliforms (TC) and Escherichia coli from drinking water, was compared to the US Environmental Protection Agency (EPA)-approved MF method (mEndo agar and nutrient agar supplemented with 4-methylumbelliferyl-β- d -glucuronide) in a collaborative study. Six wastewater-spiked Cincinnati tap water samples, containing three different concentrations of E. coli (≤ 10, 11–30, and >30 E. coli /100 ml), were analyzed concurrently by 19 geographically dispersed laboratories. Results showed that although the overall recoveries of TC and E. coli with MI agar were 12% and 26% greater, respectively, than those of the approved method, the differences were not statistically significant (α=0.05). However, the overall recovery of background/non-coliforms by the new method, 5% of the mEndo agar recovery, was significantly lower ( P =0.0009). Since the results of this study show MI agar to be equal to or better than the current method, it meets the criteria for routine compliance monitoring of drinking water.