Microbial Flora and Level of Vibrio-Parahaemolyticus of Oysters (Crassostrea-Virginica), Water and Sediment from Galveston-Bay

Aerobic plate counts at 25 degrees C of freshly harvested oysters ranged from 2.3 x 10 super(4) to 3.0 x 10 super(7) and those of sediment samples from less than 10 super(2) to 3.0 x 10 super(6)/g. Counts of water samples were nearly always less than 10 super(2) -ml. Vibrio, Aeromonas, and Moraxella spp predominated in the fresh oysters. Vibrio parahaemolyticus was isolated from 39 of 66 oyster samples and from 9 of 30 sediment and water samples. Isolation was most effective with prior enrichment of samples in trypticase soy broth with 7 per cent NaCl and subsequent plating on thiosulphate citrate bile salts sucrose agar. V. parahaemolyticus was detected in only 1 of 8 refrigerated retail oyster samples. Aerobic plate counts at 25 degrees C of refrigerated retail oysters were not much different from those of similar lots shucked under aseptic conditions in the laboratory (before shucking and washing in the plants). Aeromonas and Moraxella spp were predominant in oysters at the retail level.