Title: Characterization of Vibrio parahaemolyticus Isolated from Oregon and Washington Coastal Water and Development of Improved Methods for Vibrio

parahaemolyticus was detected in 14.3 % of oyster, 23.0 % of seawater, and 44.4 % of sediment samples with very low levels (<7.4 MPN/g) of pathogenic strains being detected in oysters. Occurrence of V. parahaemolyticus in oysters and the environments was positively correlated to water temperatures and were more frequent in sediment than in seawater or oyster. Thirty-four pathogenic V. parahaemolyticus isolated during the study were examined for virulence factors [tdh and trh genes encoding thermostable direct hemolysin (TDH) and TDH-related hemo lysis (TRH), respectively], urease production, and O-group antigenicity. The tdh and trh genes were detected in 85 % and 88 % of the isolates, respectively while almost all of them (97%) produced urease. Six O serotypes were identified among the isolates with 05 and 01 being the most prevalent. Pulsed-field gel electrolysis (PFGE) analysis of the surveyed isolates and five clinical reference strains using Notl and Sfil enzymes revealed 22 restriction patterns with NISI pattern being the most prevalent {25.6%) followed by N2S2 pattern (10.3%). Results of molecular, serological, and virulence analysis demonstrated tha