Prevalence and genetic diversity of pathogenic populations of Vibrio parahaemolyticus in coastal waters of Galicia, Spain

Summary The natural reservoirs and biological characteristics of pathogenic populations of Vibrio parahaemolyticus in marine habitats remain unclear due to difficulties in obtaining pathogenic strains from the environment. The distribution and characteristics of pathogenic V. parahaemolyticus were investigated over 1 year in three coastal environments in Galicia (Spain), includ- ing areas of the major international ports in the region. Vibrio parahaemolyticus was present in 35.3% of the samples analysed, and 535 strains were iso- lated over the period of study. Virulence genes were detected in 94 strains with diverse genetic traits: 66 trh+/tdh- ,2 4trh-/tdh+ and 4 trh+/tdh+. Different spatial and seasonal patterns were observed in rela- tion to genetic traits. The trh+/tdh- strains were detected exclusively in northern areas and prevailed in the autumn, when seawater is warmer and less saline, whereas the trh-/tdh+ strains were found in all three areas throughout winter and spring. Character- ization of potentially pathogenic strains from the envi- ronment revealed an unexpectedly diverse array of serotypes and pulsed-field gel electrophoresis (PFGE) profiles (pulsotypes) that were unrelated to clinical strains of V. parahaemolyticus that are preva- lent in Spain. The results of the current study provide a novel view of V. parahaemolyticus in Europe, in which diverse pathogenic groups are constitutive components of the environmental populations in coastal habitats.