Aims: Vibrio parahaemolyticus is a marine and estuarine bacterium that has been documented as the causative agent of food-borne outbreak worldwide. The aim of this study was to confirm the identification of presumptive V. parahaemolyticus isolates to the species level by using PCR targeted to the outer membrane protein regulation operon gene (toxR) and to investigate antibiotic resistance, plasmid profile, and the main core virulence genes of thermostable direct hemolysin (tdh) and tdh-related hemolysin (trh). Methodology and results: A total of 56 presumptive isolates of V. parahaemolyticus were isolated from seawater collected during year a 2010 sampling pilot study performed along the Arabian Gulf coast of the Eastern Province of Saudi Arabia. The purpose of this study was to confirm the identification of presumptive V. parahaemolyticus isolates to the species level by using PCR targeted to the toxR gene and to investigate antibiotic resistance, plasmid profile, and the main core virulence genes of tdh and trh. The toxR-specific PCR assay revealed that a total of 30 out of 56 isolates tested positive for V. parahaemolyticus. None of the 30 strains of the toxR gene were tested positive for tdh and trh genes. All (100%) of isolates were highly resistant to amikacin, cefuroxime, ampicillin, ticarcillin, cefaclor (80%), and tetracycline (70%). The multiple antibiotic resistance (MAR) index was measured for all 16 antimicrobial agents, and the high ranged from 0.25 to 0.56. Among the isolated V. parahaemolyticus, 22 out of 30 strains contained plasmid DNA bands ranging in size from 1.5 to 55 kb and no correlation was observed between the plasmid profiles and antibiotic resistance patterns. Conclusion, significance and impact of study The results obtained in this study indicate that V. parahaemolyticus is present in the coastal environment of the Eastern Province of Saudi Arabia.

The bacterium, Vibrio parahaemolyticus was isolated from 776 patients at Hat Yai Hospital in Southern Thailand from 2006 to 2010. 51.3–73.6% of the isolates were tdh⁺ trh⁻ and Group-specific PCR positive pandemic strains. A comparison of the number of V. parahaemolyticus isolates in this study and that from the same hospital in 2000–2005 indicates that this region of Thailand is endemic for V. parahaemolyticus.