Molecular evidence of clonal Vibrio parahaemolyticus pandemic strains

The upsurge in worldwide incidence of Vibrio parahaemolyticus infection in the last 5 years has been attributed to the recent appearance of three sero types with pandemic potential: O3:K6, O4:K68, and O1:K untypeable (KUT). Th irty-five strains of these serotypes, isolated from different countries ove r 4 years, were characterized by ribotyping and pulsed-field gel electropho resis to determine their origin. The ribotypes of the strains of these sero types were indistinguishable, except for a Japanese tdh-negative O3:K6 stra in and a U.S. clinical O3:K6 isolate, which had slightly different profiles . The migration patterns of the Notl-digest of the total DNA of the strains were similar, and only slight variations were observed between the serotyp es. By contrast, the O3:K6 and Of:KUT strains isolated before 1995 and stra ins of other serotypes had markedly different profiles. The O4:K68 and O1:K UT strains most likely originated from the pandemic O3:K6 clone.