Molecular detection of pira/b gene from vibrio parahaemolyticus isolated from shrimps in kota bharu wet markets

An abstract of the research paper presented to the Faculty of Veterinary
Medicine, University Malaysia Kelantan, in partial requirement of the course DVT 55204
- Research Project.
Acute Hepatopancreatic Necrotic Disease (AHPND) is a severe bacterial
infection in shrimp aquaculture, caused by pathogenic strains of Vibrio
parahaemolyticus harboring the plasmid-borne pirA and pirB toxin genes. While studies
on AHPND detection, genetics and outbreaks have been conducted in Asia, data on the
prevalence of these pathogenic strains in Malaysian retail markets are limited. This
study aimed to detect and characterize V. parahaemolyticus, specifically screening for
AHPND-causing strains, in white shrimp (Penaeus vannamei) from wet markets in Kota
Bharu, Kelantan. Thirty fresh shrimp samples were collected randomly from three
markets. Hepatopancreas tissue was processed for bacterial culture on Thiosulfate
Citrate Bile Salt (TCBS) agar, followed by biochemical confirmation (oxidase, Triple
Sugar Iron tests). Presumptive Vibrio spp. isolates were subjected to conventional PCR
targeting the species-specific pyrH and toxR genes, with toxR amplicons sequenced for
confirmation via NCBI BLAST analysis. Confirmed V. parahaemolyticus isolates were
then screened for the pirA and pirB genes using multiplex PCR. Three isolates (from
Pengkalan Chepa market) were confirmed as V. parahaemolyticus. However, none
carried the pirA or pirB virulence genes. Therefore, while the detection of V.
parahaemolyticus highlights a potential food safety consideration, the absence of the pirA and pirB genes suggests that the sampled shrimp from these markets did not
harbor the specific virulent strain responsible for AHPND outbreaks in aquaculture.