Distribution Of Plasmid-mediated Quinolone Resistance Gene In Wastewater And Isolation Of Resistance Bacteria

Since the introduction of the first quinolone,nalidixic,quinolones are widely used in both human and veterinary medicine as broad-spectrum antibiotics.These extensive use has resulted in bacteria rapidly developing resistance to these agents.In the decades that have elapsed,scientists are keep researching new drugs to fight against the emergence of resistance.But it seems that in this war,bacteria is the one who always be a winner. Up to now,two mechanisms of quinolones resistance had been established.The quinolone resistance is mainly acquired through chromosome mutations.. The plasmid-mediated quinolone resistance (PMQR) gene which was called qnrA was first identified in a Klebsiella pneumonione from the USA in1998. and then scientists from all over the world found other four qnr genes.Besides the Qnr proteins,which can protect DNA gyrase from quinolones,there are also two additional mechanisms:the aminoglycoside acetyltransferase Aac(6’)-Ib-cr and the efflux pump Qep A. These mechanisms confer low-level resistance of quinolone and are found can spread by horizontally transfer and at the same time to facilitate the emegency of high-level resistance.So reseaching the distribution of PMQR genes in the aquate environment is a task which brooks no delay.This study mainly researched on the antibiotics resistance situation in the water environment of Jinan area and the distribution of PMQR genes to evaluate the effects of environment.We collect water samples from hospital wastewater,municipal sewage treatment plants and Xiaoqing River.And then, the total genome of all samples were prepared for quantitation of qnrA gene and16S rRNA gene.In order of the most abundant,it does: hospital wastewater,municipal sewage treatment plants and Xiaoqing River. The result also shows that qnrA gene activities positive correlation with the16S rRNA level.At the same time,753different kinds of antibiotic resistance bacteria are sellected from the above water samples.After detecting five PMQR genes in these bacterias,we found that there are371PMQR gene positive stains,the positive rate is49.26%.There are236strains that qepA gene are positive,119stains that aac(6’)-Ib-cr gene are positive,118stains that qnrS gene are positive,27stains that qnrA gene are positive and22stains that qnrB gene are positive.The experiment also makes a detection of class Ⅰ,Ⅱ,Ⅲ integron. There are548stains containing class Ⅰ integron,16stains containing class Ⅱ integron and no strains containing class Ⅲ integron.In the following detection of the gene cassettes to the bacteria with integron,22different gene cassette arrays are found.We also analyzed the overall structure of microbiota in water samples by pyrosequencing16S rRNA genes.There are no significant differences in the diversity of species between five sampling locations.The municipal sewage treatment plants had the highest richness of species.The dominant phylum of all samples are Proteobacteria and Bacteroidetes.In all samples, the abundant genus were acinetobacter,Flavobacterium, Bacteroides,pseudomonas and Arcobacter.Rheinheimera and Cloacibacterium are associate with qnrA gene.