Relationships between Environmental Factors and Pathogenic Vibrios in the Northern Gulf of Mexico

Although autochthonous vibrio densities are known to be influenced by water temperature and salinity, little is understood about other environmental factors associated with their abundance and distribution. Densities of culturableVibrio vulnificus containingvvh (V. vulnificus hemolysin gene) andV. parahaemolyticus containingtlh (thermolabile hemolysin gene, ubiquitous inV. parahaemolyticus ),tdh (thermostable direct hemolysin gene,V. parahaemolyticus pathogenicity factor), andtrh (tdh -related hemolysin gene,V. parahaemolyticus pathogenicity factor) were measured in coastal waters of Mississippi and Alabama. Over a 19-month sampling period, vibrio densities in water, oysters, and sediment varied significantly with sea surface temperature (SST). On average,tdh -to-tlh ratios were significantly higher thantrh -to-tlh ratios in water and oysters but not in sediment. Althoughtlh densities were lower thanvvh densities in water and in oysters, the opposite was true in sediment. Regression analysis indicated that SST had a significant association withvvh andtlh densities in water and oysters, while salinity was significantly related to vibrio densities in the water column. Chlorophylla levels in the water were correlated significantly withvvh in sediment and oysters and with pathogenicV. parahaemolyticus (tdh andtrh ) in the water column. Furthermore, turbidity was a significant predictor ofV. parahaemolyticus density in all sample types (water, oyster, and sediment), and its role in predicting the risk ofV. parahaemolyticus illness may be more important than previously realized. This study identified (i) culturable vibrios in winter sediment samples, (ii) niche-based differences in the abundance of vibrios, and (iii) predictive signatures resulting from correlations between environmental parameters and vibrio densities.