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Pollution Characteristics Of Antibiotic Resistance Genes In Aquatic Products

Posted on:2018-02-22Degree:MasterType:Thesis
Country:ChinaCandidate:Y B BaFull Text:PDF
GTID:2321330536477228Subject:Food Science and Engineering
Abstract/Summary:PDF Full Text Request
Antibiotics play a non-substitutable role in aquaculture.Nevertheless,long term heavy use of antibiotic contribute to antibiotic resistance,thus,attract great attention to people.Antibiotic resistance genes is the crux of antibiotic resistance spread.ARGs have been found to be able to spread among bacteria via horizontal gene transfer(HGT),thus,pose a huge risk to food and human health.To date,the majority of studies focus on the ARGs in aquaculture environments,given aquacultured animals may be the direct vehicle of ARGs into human body,abundant ARGs in aquacultured animals might be a critical factor for pathogenic-bacteria to acquire resistance genes,surprisingly little is known about the ARG contaminations in aquacultured animals.In order to understand the characteristics of ARGs pollution in aquatic products more clearly,and to solve the problem of drug resistance and clinical medication.The main content of the study were summarized as follows:(1)Research of the pollution of antibiotic resistance genes in aquatic products wholesale market;(2)Occurrence of antibiotic resistance genes in aquatic products and its relationship with antibiotic residues in the southeast coastal area of China;(3)The analysis on mismatch between antimicrobial resistance phenotype and genotype of pathogenic Vibrio parahaemolyticus.(1).Research of the pollution of antibiotic resistance genes in aquatic products wholesale marketIn order to investigate the dissemination of antibiotic resistance genes(ARGs)from contaminated aquatic products in aquatic products wholesale market,this study targeted three large-scale aquatic products wholesale markets as research object and collected mixed sewage ditch sediment in and around the three markets separately as test samples.With the help of PCR,this study detected five categories,(four kinds of sulfonamides,eight kinds of tetracyclines,six kinds of ?-lactams,five kinds of chloramphenicol,and four kinds of streptomycin),in which there is a total of twenty seven kinds of ARGs.Moreover,PCR-DGGE technique was utilized to analyze the diversity of bacteria community in the sample.The results showed that seventeen kinds of ARGs were detected in aquatic products wholesale markets and they all contained multiple types of tetracyclines,sulfonamides,and streptomycin ARGs,which accounted for the conclusion that there was a great variety of ARGs types in aquatic products wholesale market and these three kinds of ARGs were major ones in aquatic products.Sample testing of sewage ditch sediment near the markets showed that ARGs in surrounding place was slightly lower than ARGs in markets,indicating that the occurrence of ARGs in markets would pollute surrounding environment by sewage discharge.Analysis of the results of DGGE profiles showed that though ARGs distributed in three aquaculture markets shared similarities,the distribution of bacterial types between three markets were great different,displaying that there was no direct relationship between the types of ARGs and bacterial types.This work noted that aquatic products wholesale market has became a important receiver of ARGs through the dissemination of ARGs from contaminated aquatic products,and this receiver would not only pollute surrounding environment by sewage discharge to some extent,particularly,resulting a huge risk to pollute aquatic products again,hence needing more attention.(2)Occurrence of antibiotic resistance genes in aquatic products and its relationship with antibiotic residues in the southeast coastal area of ChinaAntibiotic resistance genes(ARGs)are emerging environmental contaminants posing potential risks to worldwide human health.This study examined the occurrence of 37 ARG contaminations at 94 aquacultured animal samples(include 18 antibiotic test positive samples)from five southeast coastal cities of China.Furthermore,V.parahaemolyticus strains were isolated and determined the ARGs presence.The results showed that freshwater fishes exhibited more prevalent and the total relative abundance of ARGs were generally higher detected than marine fishes.tet S,str A,str B,aad A,flo R,sul I,and sul II were identified as the prominent ARGs,these seven ARGs were chosen because they were observed in all five cities and were the most frequently identified resistance determinants,with detection frequencies of these genes were all more than30%.Seven prominent ARGs were found in V.parahaemolyticus strains,suggesting that the predominant ARGs in aquacultured animals were consistent with food-born pathogenic bacteria.In general,Antibiotic test positive samples always harboured more diverse ARGs,suggesting that antibiotic residues may contribute to ARGs occurrence.Overall,this study first monitored the occurrence of ARG contaminations in aquacultured animals from five southeast coastal cities of China.On the other side,this research draws an urgent attention of the great needs to ARG contaminations in freshwater fish and suggests the importance of aquaculture environment in ARGs emergence.(3)The analysis on mismatch between antimicrobial resistance phenotype and genotype of pathogenic Vibrio parahaemolyticus.Antimicrobial resistance of pathogenic bacteria constitutes one of the most serious threats to food safety and human health.Our previous study revealed that the mismatch phenomenon between the antimicrobial resistance phenotype and genotype of Vibrio parahaemolyticus.For instance,some Vibrio parahaemolyticus isolates possessing aad A were found to be susceptible to aminoglycoside antimicrobial agents.In order to explain this phenomenon.Combined with the dominant resistance gene in aquatic products and the antibiotic resistance of Vibrio parahaemolyticus isolates in our lab,this study selected 10 Vibrio parahaemolyticus isolates harbouring aad A,which were sensitive to streptomycin,and 46 Vibrio parahaemolyticus isolates harbouring sul I or sul II,which were sensitive to sulfamethoxazole.The results showed that gene mutation of aad A in Vibrio parahaemolyticus contained 8 major types.The mutation of sul I mainly occurred in the 231 site deletion of A,sul II mainly occurred in the deletion of the 106 site A.These mutations are likely to cause the gene can not be properly encoded.The experimental results indicate that the resistance gene(ARGs)in the process of diffusion,the resistance genes of various causes such as deletion,duplication,mutation,frameshift insertion may be an important cause of bacterial strains resistant phenotype loss.For the first time,we analyzed the causes of the resistance phenotype and genotype inconsistency of Vibrio parahaemolyticus by analyzing the base mutation in the gene sequence.
Keywords/Search Tags:aquatic products, aquatic products wholesale market, antibiotic resistance gene, antibiotic, Vibrio parahaemolyticus
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