Quantification of Vibrio vulnificus in an Estuarine Environment: a Multi-Year Analysis Using QPCR

Abstract

Using a refined quantitative polymerase chain reaction assay, we compared surface and bottom water concentrations of Vibrio vulnificus with total Vibrio spp. concentrations, fecal indicator bacteria (Escherichia coli and Enterococcus sp.), and environmental parameters (salinity, temperature, chlorophyll a, and turbidity) over 4 years at a mesohaline site in the Neuse River Estuary in North Carolina. V. vulnificus was not detected when water temperature was below 20 °C and 93 % of positive samples were from salinities 10–20 psu. V. vulnificus was detected in 50 % of summer samples with peak concentrations in summer bottom waters. Significant positive correlations for V. vulnificus and temperature, salinity, and bacterial group abundance were found. Significant negative correlations with chlorophyll a were also observed. Interannual comparisons indicated a significant decrease in mean V. vulnificus since 2005, corresponding with increasing salinity due to severe drought conditions in 2007 and 2008. Total Vibrio spp. abundance also decreased in 2007 but returned to the previously observed abundance by 2008. Although a significant positive relationship between total Vibrio spp. and V. vulnificus was documented, interannual comparisons indicate that total Vibrio spp. densities may not be indicative of V. vulnificus in all environmental conditions and that long-term drought conditions may alter community composition.