A Survey of the Occurrence of Vibrio parahaemolyticus and V. alginolyticus on Mussels and Oysters and in Estuarine Waters in the Netherlands

S ummary : In a survey on the occurrence of Vibrio parahaemolyticus and V. alginolyticus on mussels and oysters and in estuarine waters in The Netherlands it appeared necessary to use at least 2 different enrichment procedures as well as isolation methods in parallel to obtain reliable results. A consistent identification of V. parahaemolyticus on biochemical grounds remains a difficult task; further research in this area is definitely required. The ligated intestinal segment technique gave inconsistent results; injection of organisms into the yolk sac of fertilized hen eggs seems to be a more reliable diagnostic procedure. Of 288 samples of mussels examined 2·4% were V. parahaemolyticus positive, 80 samples of oysters were all negative and amongst 64 water samples 4·7% were positive. V. alginolyticus was isolated in similar percentages of samples of mussels and water, but oysters were positive to an extent of 6·8%.