Improved isolation and detection of toxigenic Vibrio parahaemolyticus from coastal water in Saudi Arabia using immunomagnetic enrichment.

Abstract

BackgroundVibrio parahaemolyticus is recognized globally as a cause of foodborne gastroenteritis and its widely disseminated in marine and coastal environment throughout the world. The main aim of this study was conducted to investigate the presence of toxigenic V. parahaemolyticus in costal water in the Eastern Province of Saudi Arabia by using immunomagnetic separation (IMS) in combination with chromogenic Vibrio agar medium and PCR targeting toxR gene of species level and virulence genes.MethodsA total of 192 seawater samples were collected from five locations and enriched in alkaline peptone water (APW) broth. One-milliliter portion from enriched samples in APW were mixed with an immunomagnetic beads (IMB) coated with specific antibodies against V. parahaemolyticus polyvalent K antisera and separated beads with captured bacteria streaked on thiosulfate citrate bile salts sucrose (TCBS) agar and CHROMagar Vibrio (CaV) medium.ResultsOf the 192 examined seawater samples, 38 (19.8%) and 44 (22.9%) were positive for V. parahaemolyticus, producing green and mauve colonies on TCBS agar and CaV medium, respectively. Among 120 isolates of V. parahaemolyticus isolated in this study, 3 (2.5%) and 26 (21.7%) isolates of V. parahaemolyticus isolated without and with IMB treatment tested positive for the toxin regulatory (toxR) gene, respectively. Screening of the confirmed toxR gene-positive isolates revealed that 21 (17.5%) and 3 (2.5%) were positive for the thermostable direct hemolysin (tdh) encoding gene in strains isolated with IMB and without IMB treatment, respectively. None of the V. parahaemolyticus strains tested positive for the thermostable related hemolysin (trh) gene. In this study, we found that the CaV medium has no advantage over TCBS agar if IMB concentration treatment is used during secondary enrichment steps of environmental samples. The enterobacterial repetitive intergenic consensus (ERIC)-PCR DNA fingerprinting analysis revealed high genomic diversity, and 18 strains of V. parahaemolyticus were grouped and identified into four identical ERIC clonal group patterns.ConclusionsThe presented study reports the first detection of tdh producing V. parahaemolyticus in coastal water in the Eastern Province of Saudi Arabia.