Molecular characterization of Vibrio parahaemolyticus strains associated with foodborne illness in Florida.

Vibrio parahaemolyticus is the leading cause of bacterial seafood-based illness in the United States. Real-time PCR, pandemic group-specific PCR, ribotyping, and multilocus sequence typing were used to characterize 30 strains of V. parahaemolyticus including 11 strains associated with foodborne outbreaks in Florida and 6 known pandemic strains. Thirteen strains were positive for four pandemic group-specific PCR markers, including 5 strains associated with outbreaks in Florida. Molecular typing methods were used to further define the pandemic status of these strains because the current PCR markers are not sufficient to identify pandemic isolates. Nine of the Florida strains clustered with a majority of the known pandemic strains, based on ribotyping patterns using PvuII, but no isolated pandemic branch was formed. Using multilocus sequence typing, it was determined that 14 strains possess a previously determined pandemic sequence type. This study identified 13 novel sequence types and seven to nine novel alleles for each locus. Furthermore, the results indicate that seven of the strains from recent foodborne outbreaks in Florida are pandemic strains, and that multilocus sequence typing was the most accurate molecular method to identify these strains.