Occurrence of pathogenic Vibrio parahaemolyticus in crustacean shellfishes in coastal parts of Eastern India

Abstract Aim: The objective of the study was to isolate and characterize pathogenic Vibrio parahaemolyticus from crustacean shellfishes (crab and shrimp) commonly retailed in coastal parts of eastern India. Materials and Methods: Samples were processed by bacteriological isolation followed by biochemical characterization in Kaper’s medium. Presumptively identified isolates were confirmed by species-specific Vp-toxR polymerase chain reaction (PCR) assay. Virulence and pandemic property of the confirmed V. parahaemolyticus isolates were determined by specific PCR assays. Results: On screening of 167 samples comprising crabs (n=82) and shrimps (n=85) by the standard bacteriological cultural method, V. parahaemolyticus was presumptively identified in 86.6% (71/82) and 82.3% (70/85) of respective samples. Of these, 46 (56%) and 66 (77.6%) isolates from crab and shrimp, respectively, were confirmed as V. parahaemolyticus by biochemical characterization (Kaper’s reaction) followed by specific Vp-toxR PCR assay. About 10 isolates each from crab and shrimp was found to carry the virulence gene (tdh). It denotes that 12.2% of crab and 11.7% of shrimp in the study area are harboring the pathogenic V. parahaemolyticus. Such tdh+ isolates (n=20) were subjected for screening of pandemic genotype by pandemic group specific (PGS) - PCR (PGS-PCR) and GS-PCR (toxRS gene) where 11 (6.5%) isolates revealed the pandemic determining amplicon (235 bp) in PGS-PCR and belonged to crab (7.3%) and shrimp (6%) samples; however, 2 (2.4%) isolates were positive in GS-PCR and belonged to crab samples only. These two GS-PCR+ isolates from crab were also positive in PGS-PCR. Conclusion: The findings of the study conclusively indicated that a considerable percentage of crab and shrimp in these areas were harboring pathogenic and pandemic V. parahaemolyticus posing a public health risk in consumption of improperly processed such shellfishes. Cross contamination of other marine and fresh water market fishes by such shellfishes in these areas may provide scope for spreading this pathogen in community food chain.