Investigation into Pathogenic Vibio parahaemolyticus dynamics and Virulence determinants from Hawaiian Waters

Abstract

The pathogenic gram-negative halophilic bacterium, Vibrio parahaemolyticus, is a water-borne human pathogen indigenous to coastal marine and estuarine environments. When introduced to a human host, either by the consumption of raw or undercooked shellfish, or by exposure to an open wound, the pathogen can cause gastroenteritis, tissue infection, and, in some cases, septicemia. The risk of human infection is expected to be directly associated to the abundance of pathogenic V. parahaemolyticus. To evaluate how environmental conditions may influence the abundance of this pathogen I investigated the spatial, temporal, and environmental prevalence of Vibrio parahaemolyticus in the Ala Wai Canal and surrounding waters of Honolulu, Hawai’i. Strains of V. parahaemolyticus were isolated on selective media along an environmental gradient and at frequencies ranging from months to hours. Putative V. parahaemolyticus isolates were identified using chromogenic media. Their identities were later confirmed using molecular methods, and they were analyzed for the presence of known virulence-associated genes. The species-specific(tlh) gene was found in 79% of the putative V. parahaemolyticus isolates, but none of these were positive for a virulence-associated gene (tdh). There was a positive correlation between total V. parahaemolyticus abundance and salinity, but only in the range from 2.5-19 ppt. No significant correlation was found between temperature and V. parahaemolyticus abundance. Highest V. parahaemolyticus densities were usually found at the head of the canal and at the mouths of the two streams feeding into the canal (stations 1-6, 9 and 12). This information may prove useful for modeling pathogen dynamics in tropical coastal environments.