Interrelationships of environmental factors, Vibrio parahaemolyticus, and other bacteriological indices of oysters, water, and sediment from the Gulf of Mexico

A total of 153 samples of oysters, water, and sediment were tested for the presence of V. parahaemolyticus. Standard Plate Counts of the oysters ranged from 5.0e3 to >3.0e7 per g. Aerobic Plate Counts ranged from 3.0e3 to >3.0e7 per g. Bacteriological indices (coliform, fecal coliform, and E. coli counts) were not indicative of V. parahaemolyticus levels. Examination of plankton for presence of V. parahaemolyticus showed the organism to be present both in phytoplankton and in zooplankton in significantly high numbers. Market surveys indicated that V. parahaemolyticus counts of oysters usually decreased during processing. Standard Plate Counts and Aerobic Plate Counts of processed oysters increased in the majority of samples after storage at refrigeration temperatures. From the samples of oysters, water, sediment, and plankton, 2,218 isolates were picked as suspect V. parahaemolyticus. V. parahaemolyticus was present in 55.6% of the oyster samples, 45.9% of the waters, and 70% of the sediment samples. Only 0.18% of the V. parahaemolyticus isolates were Kanagawa positive. No definite seasonal effect on level of V. parahaemolyticus was apparent