Pandemic Vibrio parahaemolyticus O3:K6 Spread, France

To the Editor: Vibrio para-haemolyticus is a halophilic bacterium that occurs naturally in aquatic environments worldwide. It causes one of the most severe forms of gas-troenteritis and is the leading cause of seafood-associated bacterial gastroen-teritis in the world, often associated with the consumption of raw or under-cooked seafood. Since 1996, the incidence of V. parahaemolyticus infections has increased dramatically. V. parahaemolyticus strains previously associated with only sporadic cases of gastroenteritis have caused large-scale outbreaks in North America and epidemics in India, Southeast Asia, and Japan (1). This increase in incidence appears to be related to the emergence of a new clone, belonging to the O3:K6 serovar, which has pandemic potential. This clone was named the new O3:K6 clone to distinguish it from strains belonging to this serovar isolated before 1996, which are less pathogenic. We report the first evidence for the presence in France and suggest the presence and persistence in French coastal areas of this pandemic O3:K6 serovar, which is indistinguishable from the O3:K6 clone isolated in Bangladesh in 1996. We analyzed 13 clinical isolates of V. parahaemolyticus collected in France from 1997 to 2004 and sent to the National Reference Center (Table). All isolates were characterized by polymerase chain reaction (PCR) to detect the genes encoding the virulence-associated hemolysins, thermostable-direct hemolysin, and thermostatable-related hemolysin (2), and 2 other genetic markers, toxRS and orf8 (1,3). We also carried out molecular typing by various methods, including ribotyping, pulsed-field gel electrophoresis (PFGE), and arbitrarily primed PCR. Strains were initially identified by biochemical and cultural methods. Strain identities were confirmed by species-specific R72H PCR (4). The slide agglutination test was performed to determine whether the isolates belonged to the O3:K6 serovar. Two pandemic strains of the new O3:K6 clone and 1 strain of the old O3:K6 clone were included as external controls. Five strains were identified as V. parahaemolyticus O3:K6 by slide agglutination test. With the exception of the strain referred to as old O3:K6 clone, all O3:K6 strains studied, whether isolated in France or included as controls, were positive for tdh, toxRS, and orf8 genes. Likewise, all strains, except the old O3:K6 clone, produced BglI rRNA gene restriction patterns identical to those of a major R4 ribotype previously described (5) and were genetically indistinguishable by arbitrarily primed PCR analysis. With the exception of the strain belonging to the old O3:K6 clone, the PFGE-typeable O3:K6 strains, despite having slightly different NotI patterns …