Occurrence Of Antibiotic Resistance Genes And The Relationship With Indicator Bacteria In Haihe River,Tianjin

Objective:This work researched temporal and spatial distributions of ARGs and their relationship with indicator microorganisms.The Haihe River is one of the most serious polluted rivers in the seven water systems,and the potential ecological risk of ARGs pollution will become more and more popular.Methods:In the present work,we investigated the prevalence of 24 ARGs active against eleven antibiotic classes(aminoglycosides(aph(2'')-Id?aadA?aac(6')-Ib),quinolones(qnrA?gyrA),?-lactams(blaTEM?ampC?blaNDM-1),sulfonamides(sul1?sul2?sul3),chloramphenicols(catA?clmA),macrolides(erm A?erm B),tetracyclines(tetA?tetB?tetC?tetM?tetQ),isoniazid(katG),rifampicin(rpo B),trimethoprim(dfrA1),and vancomycin(vanA))in surface water samples collected from seven sites in the Haihe River over a 1-year period.Real-time PCR was applied to quantify ARG-based pollution and variability in seasonal thermotolerant coliform and Escherichia coli was investigated and correlated with the distribution of ARGs.Results:(1)In this study,we found 24 genes could be detected by real-time quantitative PCR,and the sul1 gene was the dominant resistance gene,and the total average abundance was 6.4×10~9 copies/m L.The statistical analysis showed that the relative abundance of bla NDM-1 was greater in summer than in spring and autumn,and the relative abundance of aph(2'')-Id and qnrA was greater in summer than in winter.The relative abundance of tetQ was significantly higher in the downstream than that in the upstream,while the other genes were not significantly differences in the temporal and spatial distribution.(2)Analysis of two kinds of water pollution indicator index to obtain,thermotolerant coliform detection rate reached 97.56% and Escherichia coli detection rate reached 95.12%.There were significant differences between thermotolerant coliform and Escherichia coli in different regions,and the number of colonies was higher in downstream than that in midstream and upstream.There were significant differences between thermotolerant coliform and Escherichia coli in different seasons,and the number of colonies in summer and autumn was higher than that in winter and spring.(3)Correlation analysis showed that ermB?aac(6')-Ib?clm A? aadA?qnrA?sul3?tetB?tetC?tetM?tetQ?katG?rpoB?vanA and thermotolerant coliform and Escherichia coli were significantly correlated,no correlation between other genes.Indicator bacteria play an important role in the temporal and spatial distribution distribution of the ARGs.Conclusion:There have detected ARGs and indicator bacteria contamination in water environment in Haihe River and occurred a correlation between the indicator bacteria and most of the resistance genes.This study will enhance the understanding of the ecological risk of ARGs,and further enrich the study of resistance genes in Tianjin Haihe River.