Monitoring And Exposure Assessment Of Drug Resistance Of Vibrio Parahaemolyticus In Commercial Shrimps

Shrimp is the most important seafood in South Asia and Southeast Asia.It is loved by people for its rich nutrition and delicious taste.Shrimp is a carrier of foodborne pathogens because of its rich nutrients.Vibrio parahaemolyticus?VP?is one of the world's foodborne pathogenic bacteria,which is the main cause of diarrhea,gastroenteritis and other diseases.Due to irrational and excessive use of antibiotics,they lead to drug resistance and even multidrug-resistant strains?MDRO?.Therefore,monitoring the diversity of resistant bacteria in shrimp is the key to control the use of antibiotics and ensure food safety.At present,the application of the diversity detection of drug-resistant bacteria in aquatic products is still blank.The purpose of this study is to study:1)Detection of drug-resistant bacterial diversity in shrimp,so as to accurately monitor the diversity of drug-resistant bacteria in shrimp.2)There is still a lack of rapid detection and exposure assessment of the drug resistance of Vibrio parahaemolyticus.3)Meanwhile,the heterogeneity of multidrug-resistant strain was studied and the basic data were provided for the risk assessment of drug-resistant bacteria.1)Detection of drug-resistant bacterial diversity in shrimpIn order to study the drug resistance and pollution of Sulfadiazine,Tetracycline and Streptomycin in shrimp,the aquatic products market of 3 major cities in Shanghai?Caoyang,Dongfang International,Hengda?was selected as the research object,The diversity of resistant bacteria in the samples was detected by PCR-DGGE and the diversity of antibiotic resistance genes?ARGs?was detected by PCR.The results show Vibrio.sp was the most dominant bacterial genus in sulfadiazine resistant bacteria?44.9%of the total resistant bacteria?,tetracycline resistant bacteria?38.2%of the total resistant bacteria?and streptomycin resistant bacteria?41.1%of the total resistant bacteria?,The nunber of resistant bacteria decreased with the increase of antibiotic concentration.In freshwater shrimp,vibrio and aeromonas were dominant bacteria,accounting for 29.16%and 25.32%respectively;the genus vibrio is 57.07%of the total resistant bacteria of sea shrimp.sulI,sulII and str B resistance genes were detected in all resistant bacteria,and tet A,tetB,and strA resistance genes were detected in most resistant bacteria,the resistance genes sulII,tetW,tetM and tetK were not detected.The Shannon-Wiener index?H'?of diversity found that there was a significant difference?p<0.05?in the microbial community between shrimps samples from major aquatic markets.There is no cross contamination of shrimp from the farms to the aquatic products market,suggesting that secondary pollution in the aquatic product market may lead to microbial diversity.2)Comparison of antimicrobial resistance of Vibrio parahaemolyticus isolated from different sourcesIn order to compare the differences in antimicrobial resistance between different sources and different pathogenic Vibrio parahaemolyticus,the antibiotic resistance of 44V.parahaemolyticus strains was detected by modified K-B disk method,and antimicrobial resistance genes?ARGs?were detected by PCR.The results showed that there were no significant differences in antimicrobial resistance phenotype between seawater and freshwater shrimp isolates,and the antimicrobial resistant rates were 100%and 95.5%respectively;However,the multidrug resistance of pathogenic strains reached73.7%,significantly higher than that of non-pathogenic strains?16%?.The type and number of ARGs between different sources and different pathogenic strains also has no significant differences.This study provides the basic data for the drug resistance diversity of V.parahaemolyticus,and provides relevant help for further study of antimicrobial resistant bacteria risk assessment.3)Comparative study on growth heterogeneity of antimicrobial resistant Vibrio parahaemolyticusCompare the maximal specific growth rate and growth rate of 17 strains of Vibrio parahaemolyticus with different drug resistance,drug-resistant phenotype and genotype incongruent in alkaline peptone water?APW,3%NaCl?at different temperatures?10,20,30,37??.The maximum specific growth rate of Vibrio parahaemolyticus was determined by Bioscreen C automatic microorganism growth curve analyzer.The growth curves of different temperatures were constructed and the growth kinetic parameters were obtained by using the modified Gompertz model.There was a certain difference between different drug resistant Vibrio parahaemolyticus,and the difference increased with the decrease of temperature.The more variety of antibiotic resistance,the bigger the?_max was.At the same temperature,there was a certain difference in the growth parameters between the resistant phenotype and the genotype incongruent Vibrio parahaemolyticus.However,there was no significant correlation between the growth parameters of the strains and the inconsistency of the resistant phenotype and genotype of the strain.The heterogeneity of microbial growth kinetics parameters between strains will affect the accuracy of risk assessment.This results can provide basic data support for the risk assessment of multi-drug resistant Vibrio parahaemolyticus.