49B-23 |
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J. DUAN and Y.-C. Su. Dept. of Food Science & Technology, Oregon State Univ., 100 Wiegand Hall, Corvallis, OR 97331-6602 Vibrio parahaemolyticus is a human pathogen that occurs naturally in estuaries and molluscan shellfish. It can cause acute gastroenteritis and septicemia in humans through the consumption of raw shellfish, particularly oysters. This study investigated incidences of V. parahaemolyticus in Oregon and Washington oyster growing environment and provided information of microbial hazards associated with oyster produced in the Pacific Northwest region. A total of 252 samples including seawater, estuary water, sediment, and oyster were collected from three oyster farms in Oregon and Washington between November 2002 and October 2003. The densities of V. parahaemolyticus in samples were analyzed with 3-tube most probable number (MPN) method and confirmed by a multiplex polymerase chain reaction (PCR) targeting tl, tdh and trh genes. V. parahaemolyticus was detected in 28% of samples with total populations ranging from 3 to 1100 MPN per 100 ml or g of sample. Pathogenic strains (positive for tdh or trh gene) were detected in 12% of samples with densities ranging from 3 to 43 MPN per 100 ml or g of sample. The densities of total and pathogenic V. parahaemolyticus were both higher in the summer months (July to September) and appeared to be related to water temperatures. Approximate 73% of Vibrio containing samples were collected when water temperatures were higher than 15°C. There was no apparent correlation between the occurrence of V. parahaemolyticus and water salinity. This study showed low incidences of pathogenic V. parahaemolyticus in Oregon and Washington oyster growing environment. However, higher contamination in oysters can occur during summer months. Oysters intended for raw consumption should be cooled down rapidly to refrigeration temperatures after harvest and stored at low temperatures until consumption.
Session 49B, Aquatic Food Products: General
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