Incidence and detection of pathogenic Vibrio sp. in a northern New EnglandEstuary, USA

Many Vibrio species are capable of causing infections in humans. Vibrio vul nificus and Vibrio parahaemolyticus are part of the normal microflora of es tuaries and have been implicated in diseases from consumption of raw or und ercooked shellfish. In the Great Bay Estuary of Maine and New Hampshire, oy sters (Crassostea virginica) and soft-shell clams (Mya arenaria) are harves ted for commercial and recreational purposes. Only one incidence of V. para haemolyticus infection from shellfish consumption has been documented. Trad itional methods and a gene probe assay were used to enumerate V. vulnificus in water from sites along salinity gradients from two tributaries to the m ain water body (Great Bay) of the estuary. V. parahaemolyricus, Escherichia coli, enterococci, fecal coliforms, nitrate, ammonium, orthophosphate, sus pended solids, chlorophyll a, dissolved organic carbon (DOC), temperature, and salinity were also measured. Results showed lower salinity and higher c oncentrations of dissolved nutrients, suspended solids, fecal indicator bac teria, and chlorophyll a in tributaries compared to Great Bay. Both Vibrio sp. were detected more frequently and at higher concentrations in the tribu taries. Multiple regression analysis suggested suspended solids were the mo st significant variable, accounting for similar to 27% of the variance in V . vulnificus and V. parahaernolyticus concentrations. However, the gene pro be results showed DOC was the most significant variable for explaining (44% ) the variance in V. vulnificus concentrations. The results suggest that im proved detection methods can enhance the understanding of environmental con ditions conducive to both growth and inhibition of these pathogens.