| Vibrio parahaemolyticus is one of the most most important food-borne pathogens, and the leading cause of diarrheal disease throught the world. Antibiotic resistance genes which spread in the environment resulting in antimicrobial resistance increase the risk of V. parahaemolyticus. Studying on the distribution, antimicrobial resistance and genetic of V. parahaemolyticus could make a contribution to completely understand basic information of V. parahaemolyticus, and provide data for controlling the prevalence and antimicrobial resistance of V. parahaemolyticus. Therefore, in order to solve the antimicrobial resistance of V. parahaemolyticus, some researches has been done as follows:(1) Antimicrobial resistance of Vibrio spp. from shrimp ponds in Shanghai;(2) Mismatch between antimicrobial resistance phenotype and genotype of V. parahaemolyticus from seafood in Shanghai;(3) Virulence genes, antimicrobial resistance and genetic diversity of V. parahaemolyticus from municipal hospital in Shanghai;(4) Compare the antimicrobial resistance among V. parahaemolyticus of different sources;(5) Growth kinetic parameters of multi-drug and single-drug resistant V. parahaemolyticus strains in pure culture and in Penaeus vannamei.(1) Antimicrobial resistance of Vibrio spp. from shrimp ponds in ShanghaiThis study investigated the distribution, antimicrobial resistance and genetic diversity of Vibrio spp. from shrimp ponds in Shanghai. The results showed that the detection rate of V. parahaemolyticus and V. cholera were 100% in all samples, suggesting the serious pollution of Vibrio spp. occurred in shrimp ponds. There were 28 sequence typing of V. parahaemolyticus in shrimp ponds of Shanghai, and 92.9% were no reported previously, including two major colone group CC1420 and CC744. V. cholera had 43 STs, and 41 were new found. The results demonstrated that high genetic diversity of Vibrio spp. in shrimp ponds. In addition, there were lots of ARGs in water of shrimp ponds, and this may be the reason for the increase of antimicrobial resistance of Vibrio spp.. This study firstly study on the dynamic change of antimicrobial resistance of Vibrio spp., and provided the basic data for controlling the development and transimition of antimircrobial resistance of Vibrio spp..(2) Mismatch between antimicrobial resistance phenotype and genotype of V. parahaemolyticus from seafood in ShanghaiAntimicrobial resistance phenotypes(18 antimicrobials; disk diffusion method) and genotypes(38 antimicrobial resistance genes; PCR) of 20 pathogenic Vibrio parahaemolyticus strains isolated from seafood in Shanghai wholesale markets between 2009 and 2013 were evaluated. Seventeen isolates(85%) were resistant to one or more antimicrobials, and highest resistance was observed to ampicillin(85%) and cephazolin(30%). And the isolates with tdh displayed higher resistant rates than isolates with trh. Eight antimicrobial resistance genes(strB, aadA2, strA, tetA, floR, sulI, sul II, and sulIII) were detected in these isolates. Surprisingly, the antimicrobial resistance phenotypes and genotypes of these isolates were not consistent: some isolates were resistant to β-lactam or aminoglycoside, whereas the corresponding genes were negative. Comparatively, aminoglycoside, tetracycline and chloramphenicol resistance genes occurred in susceptibility isolates. This research reveals the mismatch phenomenon between the antimicrobial resistance phenotype and genotype of seafood-derived pathogenic V. parahaemolyticus, and that susceptibility isolates might be a potential risk source for storage and transmission of resistance genes.(3) Virulence genes, antimicrobial resistance and genetic diversity of V. parahaemolyticus isolated from municipal hospital in ShanghaiThis study analyzed the virulence genes, antimicrobial resistance of 42 V. parahaemolyticus isolated from municipal hospital in Shanghai, and the Multilocus Sequence Typing approach(MLST) was employed to reveal the genetic diversity of these isolates. The results showed the isolates with tdh-positive were the leading cause of V. parahaemolyticus infection in Shanghai. The antimicrobial resistance V. parahaemolyticus clinical isolates was serious, and the ratio of multi-drug resistant strains was 50%. The Clonal Complexes 655 was determined as the dominant group among 42 isolates, and should be payed more attention in future research.(4) Comparison of the antimicrobial resistance among V. parahaemolyticus of different sourcesThis study analyzed the antimicrobial resistance and genetic diversity of 42 V. parahaemolyticus isolated from different sources. The results showed that there were no significant difference between the strains from aquclture and cilinical phase. CC655 was the major clone group of cilininal V. parahaemolyticus in Shanghai. The antimicrobial resistance rate of cilinical strains was higher than that of seafood. The reason may be that ARGs horizontally transferred in human intestinal tract which lead to the development of antimicrobial resistance.(5) Growth kinetic parameters of multi-drug and single-drug resistant V. parahaemolyticus strains in pure culture and in Penaeus vannameiThe variations in growth kinetic parameters of single- and multi-drug resistant V. parahaemolyticus strains were investigated, and the relationship between bacterial resistance and risk was explored. A Bioscreen-C automated growth curve analysis system combined with the serial dilution method was employed to compare and analyze the maximum specific growth rates(μmax) of V. parahaemolyticus strains with varying degrees of drug resistance cultured in trypticase soy broth(TSB). Furthermore, Penaeus vannamei was inoculated with the VPD18 strain, which is resistant to six antibiotics, and the VPD43 strain, which is only resistant to ampicillin. Growth curves at different temperatures were established and then the growth dynamics parameters were calculated using the Baranyi model. There was no significant difference in μmax values between the single- and multi-drug resistant strains grown in TSB(p > 0.05). However, in P. vannamei, the μmax of the single-drug resistant strain was higher than that of the strain resistant to six antibiotics, but the latter strain had a shorter lag time(λ). These results suggest that the increase of antibiotic resistance may lead to a shortened λ, but has no significant effect on the μmax. The results of this study can provide basic data for the development of a quantitative risk assessment of V. parahaemolyticus in China. |
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