Synthetic oligodeoxyribonucleotide probes to detect Kanagawa phenomenon-positive Vibrio parahaemolyticus.

Synthetic oligodeoxyribonucleotide probes were used in the colony hybridization test to examine the association between the Kanagawa phenomenon (KP) and the thermostable direct hemolysin gene (tdh) of Vibrio parahaemolyticus. Representative V. parahaemolyticus strains with a variety of KP reactions and 17 other Vibrio species were examined for homology with four synthetic oligodeoxyribonucleotide probes (19 to 21 bases long) representing different regions of the tdh structural gene. Under stringent conditions, two of the probes were capable of distinguishing KP-positive V. parahaemolyticus from KP-negative or KP weak-positive V. parahaemolyticus which possesses mutated tdh genes. Vibrio hollisae strains hybridized with all four probes under reduced stringency, suggesting that they have tdh-related genes which are homologous but not identical to the tdh gene in all the regions examined. The results suggest that the colony hybridization test with the synthetic oligonucleotide probes is more suitable for the definitive determination of KP-positive strains than the hybridization with the larger gene probe or immunological assays.