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

Background:Vibrio parahaemolyticusis recognized globally as a cause of foodbornegastroenteritis and its widely disseminated in marine and coastal environmentthroughout the world. The main aim of this study was conducted to investigate thepresence of toxigenicV. parahaemolyticusin costal water in the Eastern Province ofSaudi Arabia by using immunomagnetic separation (IMS) in combination withchromogenic Vibrio agar medium and PCR targetingtoxRgene of species level andvirulence genes.Methods:A total of 192 seawater samples were collected fromfive locations andenriched in alkaline peptone water (APW) broth. One-milliliter portion fromenriched samples in APW were mixed with an immunomagnetic beads(IMB) coatedwith specific antibodies againstV. parahaemolyticuspolyvalent K antisera andseparated beads with captured bacteria streaked on thiosulfate citrate bile saltssucrose (TCBS) agar and CHROMagar Vibrio (CaV) medium.Results:Of the 192 examined seawater samples, 38 (19.8%) and 44 (22.9%) werepositive forV. parahaemolyticus, producing green and mauve colonies on TCBS agarand CaV medium, respectively. Among 120 isolates ofV. parahaemolyticusisolatedin this study, 3 (2.5%) and 26 (21.7%) isolates ofV. parahaemolyticusisolatedwithout and with IMB treatment tested positive for the toxin regulatory (toxR) gene,respectively. Screening of the confirmedtoxR 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 theV. parahaemolyticusstrains tested positive for the thermostablerelated hemolysin (trh) gene. In this study, we found that the CaV medium hasno advantage over TCBS agar if IMB concentration treatment is used duringsecondary enrichment steps of environmental samples. The enterobacterial repetitiveintergenic consensus (ERIC)-PCR DNAfingerprinting analysis revealed highgenomic diversity, and 18 strains ofV. parahaemolyticuswere grouped and identifiedinto four identical ERIC clonal group patterns.Conclusions:The presented study reports thefirst detection oftdhproducingV. parahaemolyticusin coastal water in the Eastern Province of Saudi Arabia.