Occurrence of Vibrionaceae in natural and cultivated oyster populations in the Pacific Northwest.

Studies were done to assess the role of oysters from the Pacific Northwest as a potential source of Vibrionaceae. Oysters collected from natural and cultivated populations on the British Columbia Coast were opened using sterile instruments. The gills and oyster meat were each removed, and the meat was cut in half. The gills and the cut surface of the oyster meat were each cultured by inoculating them directly to the surface of agar plating media for the isolation of Vibrionaceae. Overall, 120 oysters were cultured, and 60 yielded Vibrionaceae. Vibrio parahaemolyticus, Vibrio fluvialis, and Vibrio vulnificus were the most commonly isolated organisms. Vibrionaceae were most often recovered from oysters collected under warm-water conditions from natural stocks (83% positive), followed by oysters from the same sites collected under cold-water conditions (35% positive). Only 29% of oysters collected from cultivated commercial stocks under warm water conditions yielded Vibrionaceae, and no Vibrionaceae were isolated from oysters collected from these sites during periods when water temperatures were low. The results suggest that oysters are a significant source of potentially pathogenic Vibrionaceae in the Pacific Northwest. However, the risk of exposure to these bacteria can be reduced by consumption of cultivated oysters harvested under cold-water conditions.