Isolation and characterization of pandemic and nonpandemic strains of Vibrio parahaemolyticus from an outbreak of diarrhea in North 24 Parganas, West Bengal, India.

Strains of the enteric pathogen Vibrio parahaemolyticus harboring the thermostable hemolysin (TDH) encoding gene tdh is known to cause epidemic and pandemic diarrhea. In industrialized countries, this pathogen causes sporadic or outbreaks of diarrheal illness associated with consumption of raw or improperly cooked seafood. This report describes a foodborne outbreak of gastroenteritis caused by V. parahaemolyticus in June 2011 following consumption of food served at a funeral reception held at Habra, North 24 Parganas, West Bengal, India. About 650 people attended the function, of whom 44 had acute watery diarrhea with other clinical symptoms; 35 of them were admitted to the District Hospital for the rehydration treatment. Stool specimens collected from three hospitalized cases were positive for V. parahaemolyticus, of which two strains were identified as an O4:K8 serovar and one was identified as O3:K6 serovar. The O3:K6 strain also possessed the pandemic group-specific toxRS gene target (GS), whereas the O4:K8 strains were negative. All strains were polymerase chain reaction-positive for tdh but were polymerase chain reaction-negative for trh. All of the strains were resistant to ampicillin but were pansensitive to other antimicrobials tested. Pulsed-field gel electrophoresis (PFGE) analysis using NotI showed that the O3:K6 strain was similar to that of a recent clinical strain from Kolkata, but had diverged from other strains during previous years. In contrast, PFGE analysis showed that the O4:K8 strains were closely related but differed from the Kolkata strain.