Characteristics of Vibrio parahaemolyticus O3 : K6 from Asia

A variety of serovars of the food-borne pathogen Vibrio parahaemolyticus no rmally cause infection. Since 1996, the O3:K6 strains of this pathogen have caused pandemics in many Asian countries, including Taiwan. For a better u nderstanding of these pandemic strains, the recently isolated clinical O3:K 6 strains from India, Japan, Korea, and Taiwan were examined in terms of pu lsed-field gel electrophoresis (PFGE) typing and other biological character istics. After PFGE and cluster analysis, all the O3:K6 strains were grouped into two unrelated groups. The recently isolated O3:K6 strains were all in one group, consisting of eight closely related patterns, with I1(81%) and I5(13%) being the most frequent patterns. Pattern Il was the major one for strains from Japan, Korea, and Taiwan. All recently isolated O3:K6 strains carried the thermostable direct hemolysin (tdh) gene. No significant differ ence was observed between recently isolated O3:K6 strains and either non-O3 :K6 reference strains or old O3:K6 strains isolated before 1996 with respec t to antibiotic susceptibility, the level of thermostable direct hemolysin, and the susceptibility to environmental stresses. Results in this study co nfirmed that the recently isolated O3:K6 strains of V. parahaemolyticus are genetically close to each other, while the other biological traits examine d were usually strain dependent, and no unique trait was found in the recen tly isolated O3:K6 strains.