Aerobic plate counts at 25 C of freshly harvested oysters ranged from 2.3 × 104 to 3.0 × 107 and those of sediment samples from <102 to 3.0 × 106/g. Counts of water samples were nearly always <102/mi. Vibrio, Aeromonas, and Moraxella species 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% NaCl and subsequent plating on thiosulfate citrate bile salts sucrose agar. V. parahaemolyticus was detected in only 1 of 8 refrigerated retail oyster samples. Aerobic plate counts at 25 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 species were predominant in oysters at the retail level.
aPublished with the approval of the Director of the Texas Agricultural Experiment Station, College Station.