Background & aim: Vibrio parahaemolyticus is a Gram negative halophilic bacterium found in aquatic environments. This bacterium has been introduced as a cause of acute gastroenteritis following the consumption of raw and uncooked seafood. Major symptoms of Vibrio parahaemolyticus illness is watery diarrhea, abdominal cramps, Nausea, Vomiting, Fever, Headache and Bloody diarrhea. The purpose of this study was isolation and identification of Vibrio parahaemolyticus from Persian Gulf and the determination of their phylogenetic relationship. In addition, antibiotic susceptibility of the isolates was evaluated in order to achieve maximum information concerning a drug of choice.

Methods: In this study, 89 samples of water, sediments, fish and shrimp were collected from different regions of the Persian Gulf. All samples were asssessed for phenotypic and molecular isolation and identification of Vibrio parahaemolyticus. Then the positive and negative  strains of conagua vibrio parahaemolyticus were determined based on hemolysin production. the identification and phylogenetic relationship  were  analyzed using the mega-6 software. Finally susceptibility of Kanagawa positive Vibrio parahaemolyticus to antibiotics was evaluated by disk diffusion method and minimal inhibitory concentrations of effective antibiotics were assessed using double serial dilution method.

Results: A total of nine Vibrio parahaemolyticus were isolated and identified. Of all isolates five strains were Kanagawa positive and four were Kanagawa negative. All isolates exhibited phylogenetic relationship to each other except one strain (NSP1). The results obtained from antibiotic susceptibility of Kanagawa positive  Vibrio parahaemolyticus isolates illustrated that most of the isolates were resistance to Vancomycin, Oxacillin, and Amikacin and susceptible to Trimetoprim Sulfometaxazole respectively. In addition, the lowest Minimal inhibitory Concentration (MIC) value was found for Sulfometaxazole  and highest MIC value was found for Nitofuran.

Conclusion: The present study illustrated that both pathogenic and nonpathogenic Vibrio parahaemolyticus existed in the persian Gulf. On the other hand these bacteria that could facilitate phylogenetic relationship with each other because of  horizontal gene transfer among them.Trimetoprim Sulfometaxazole could be considered a durg of choice for treatment of the patient suffering from Vibrio parahaemolyticus infections.