PREVALENCE OF HEAT-RESISTANT VIBRIO PARAHAEMOLYTICUS IN RETAIL SEAFOOD

Abstract

Previous work using a modified two-step enrichment method recovered total Vibrio parahaemolyticus, including the regular and heat/pasteurization-resistant strains. These strains would remain undetectable by exclusive cultivation protocol, attributed to their viable-but-nonculturable (VBNC) property, from environmental shellfish seafood. Hence, this suggests the need to validate retail seafood safety from this human pathogen and reform the inspection examination and cooking protocols mandated by the regulators to mitigate vibriosis recurrence. This modified method was further explored with raw, frozen shellfish seafood products from retail stores nationwide in the US for heat/pasteurization-resistant V. parahaemolyticus using nourishment only (one-step enrichment) or nourishment and heating selection (two-step enrichment) combined, followed by selective cultivation on thiosulphate-citrate-bile-salt agar (TCBS) media. Both presumptive regular and heat-resistant V. parahaemolyticus were recovered from processed shrimps (deveined/non-deveined, shell, and tail on), and non-processed oysters and crabs. Of 29 isolates recovered, nine (31%) were confirmed as heat-resistant (two from oyster; 7%) and regular (seven, two from shrimp; five from oyster; 24%) V. parahaemolyticus using 16S rDNA bacterial identification. However, none of them were resistant to pasteurization conditions. Virulence phenotype and genotype examinations indicated the presence of hemolysis- and urease-positive V. parahaemolyticus and that their unparallel phenotype/genotype correlation could be attributed to gene manipulation. For the first time, the present study reveals the prevalence of total V. parahaemolyticus, both regular and heat-resistant pathogenic strains, in retail shellfish products using the modified two-step enrichment technique and acclaims the need to reform the investigative and cooking standard protocol of USDA and other food safety regulatory entities.