Research The Phenotypic Antimicrobial Resistance And Genotyping Traits Of Vibrio Parahaemolyticus Isolates

Vibrio parahaemolyticus(VP) is a kind of gram-negative pathogenic bacteria which can cause food poisoning. This bacteria widely exist in shellfishes, fishes, shrimps and other seafood. Resistant strains is increasing with extensive use of antibiotics.Hence, it is necessary to monitor Vibrio parahaemolyticus through the food supply chain.Sixty isolates of Vibrio parahaemolyticus from food and patiens were used in our study.The disk diffusion method was performed to determine the Antimicrobial Resistance,using 18 antibiotics, according to the latest standard M100-S22, recommended by Clinical and Laboratory Standards Institute(CLSI 2012). The results showed that the highest resistance frequency was found to ampicillin(85%), followed by cefazolin(41.7%) and cefotaxime(20%). The frequencies of resistance were all below 20% including inpiperacillin, ceftazidime, tetracycline, Amoxicillin/clavulanic acid. In contrast, all of the60 Vibrio parahaemolyticus isolates were sensitive to Piperacillin/Tazobactam, Imipenem.Cefotaxime, gentamicin, Nalidixic acid, norfloxacin, chloramphenicol.Secondly, The presence of antibiotic resistance genes in chromosome or mobile genetic elements is a strong indicator of a resistance phenotype. PCR screening was conducted for the presence of 14 genes conferring antibiotic resistance.The existence frequencies of resistance gene VP-bla were 100%.The others genes were not detected in all isolates.Thirdly, two virulence-related genes(tdh、trh) were analyzed by PCR for selected 21 isolates. The results demonstrated that 76.2(16/21) percent isolates carrying tdh, and only9.5(2/21)percent having trh gene.Finally, in order to identify the correlation and characteristics of the isolates more exactly, MLST was applied for further molecular typing. A total of 13 STs were found.ST-3 got the largest number of 8 strains which consisted of 6 clinical isolates and 2 food isolates. The analysis result of Mega software showed that ST-830 and ST-3 had a relatively high level of genetic similarity. The results demonstrated diversity of Vibrio parahaemolyticus isolates in correlation and characteristics.