Quantitative Microbial Risk Assessment of Pathogenic Vibrios in Marine Recreational Waters of Southern California

Abstract

This study investigated the occurrence of three types of vibrios in Southern California recreational beach waters during the peak marine bathing season in 2007. Over 160 water samples were concentrated and enriched for the detection of vibrios. Four sets of PCR primers, specific for Vibrio cholerae, V. parahaemolyticus, and V. vulnificus species and the V. parahaemolyticus toxin gene, respectively, were used for the amplification of bacterial genomic DNA. Of 66 samples from Doheny State Beach, CA, 40.1% were positive for V. cholerae and 27.3% were positive for V. parahaemolyticus, and 1 sample (1.5%) was positive for the V. parahaemolyticus toxin gene. Of the 96 samples from Avalon Harbor, CA, 18.7% were positive for V. cholerae, 69.8% were positive for V. parahaemolyticus, and 5.2% were positive for the V. parahaemolyticus toxin gene. The detection of the V. cholerae genetic marker was significantly more frequent at Doheny State Beach, while the detection of the V. parahaemolyticus genetic marker was significantly more frequent at Avalon Harbor. A probability-of-illness model for V. parahaemolyticus was applied to the data. The risk for bathers exposed to recreational waters at two beaches was evaluated through Monte Carlo simulation techniques. The results suggest that the microbial risk from vibrios during beach recreation was below the illness benchmark set by the U.S. EPA. However, the risk varied with location and the type of water recreation activities. Surfers and children were exposed to a higher risk of vibrio diseases. Microbial risk assessment can serve as a useful tool for the management of risk related to opportunistic marine pathogens.

Effect of Climate Change on the Concentration and Associated Risks ofVibrioSpp. in Dutch Recreational Waters

“…Computation of the risks of illness showed that the current risks of bathing associated with V. parahaemolyticus vary between locations, and range from 10 −4 and 10 −2 for an entire summer. Risks of illness for a single bathing event at the North Sea are, remarkably because geographical locations are completely different, similar to risks for two southern California recreational waters, namely, on the order of 10 −5 . Risks for the Oosterschelde and Wadden Sea were predicted to be one and two log 10 higher, respectively, mainly because of higher water temperatures at these locations.…”

A Novel Triplex Quantitative PCR Strategy for Quantification of Toxigenic and Nontoxigenic Vibrio cholerae in Aquatic Environments

“…Two V. cholerae-specific genes, ompW for total V. cholerae and ctxA for toxigenic V. cholerae, were chosen for the multiplex qPCR assay. In contrast to other published assays (4,15,27), an internal amplification control (a plasmid harboring a partial sequence of the egfp gene) was additionally included in our assay to avoid false-negative results due to PCR inhibition. A huge amount of different targets, such as hlyA, zot, ompU, ompW, ctxA, rtxA, and toxR, are currently used for the detection of V. cholerae by various qPCR assays (14,28).…”

Recreational swimmers' exposure to Vibrio vulnificus and Vibrio parahaemolyticus in the Chesapeake Bay, Maryland, USA

“…A recent quantitative microbial risk assessment of Vibrio, using modeled V. parahaemolyticus water concentrations up to 10 CFU mL −1 , estimated that, under these conditions, thirteen surfer and nine child illnesses per 1000 recreationists (surfer or swimmer) could occur, falling below the Environmental Protection Agency's benchmark for recreational exposure illnesses of 19 per 1000 for either group (Dickinson et al, 2013). Given these estimates, Vibrio concentrations measured in water during our study could compromise swimmer safety, particularly swimmers with open wounds, resulting in a number of illnesses above this benchmark level.…”