Compare Of Plasmid Resistance And Detection Of Resistance Gene QnrS To Quinolone By PCR Among Avian Escherichia Coli Strains From Shandong Province

Quinolone drugs are widely used in the treatment of systemic infectious diseases. Theuseage amout of quinolone drugs have raised in the second place, only less than the amout ofβ-lactam antibiotics. In recent years, the bacterial resistance to quinolone antibiotics is rising,and the multiple drug-resistant strains is being prevalent, especially in the common clinicaland veterinary Escherichia coli, the resistance mechanism to quinolone is becoming morecomplex. Epidemiological detection and identification of quinolone resistance plasmids in E.coli, will be helpful to further understand the molecular mechanism of bacterial resistancequinolone drugs and benefit for guiding clinical treatment.1.Dection of quinolone resistance gene qnr in E. coliIn order to study the prevalent of resistance genes in plasmid to quinolone among avian E.coli Strains from Shandong province, a total of230strains isolated in2004-2011were testedby PCR to examine the qnrA, qnrB and qnrS genes which mediated quinolone resistance. Theresults indicated that the present ratio of qnrA, qnrB and qnrS genes were0,0and25.22%(58/230), We found16positive E coli from24qnrS positive by PCR after sequencing(16/24),8were negative(8/24). The homology of16positive bacterial strains and JF773350(GenebankTM) were among98.1%-98.8%, and there was high false positive rate in detectionof qnrS gene (8/24) by sequencing some PCR positive samples.16positive sequences havebeen submitted to the GeneBank nucleotide sequence database accession number wereJQ993348to JQ993363. In order to improve the specificity of detection of qnrS gene, anested-PCR method was established and used to detect the230E. coli strains. The sequencingresults indicted that the accuracy of the method was100%, and the the present ratio of qnrSgene was16.52%(38/230), which showed that the quinolone resistance plasmid with qnrSgene was more widely distributed in avian E. coli Strains from Shandong province.2. Compare and detection of quinolone resisitance plasmid Eight E. coli strains (EDFF, YDA38, MJ071107, TZ-A, ED127, ED437, TAJ-1and ED039)were selected for extracting plasmids by SDS alkaline lysis method, then the plasmids weretransformed into DH5α, respectively. In order to make sure the steady heredity of theplasmids, repeat the steps in three times. A total of8strains which were deliverd by resistanceplasmid were tested by K-B (Kirby-Bauer) method to analyze the quinolone susceptibility (33kinds of drugs), by micro-dilution method to evaluate the MICs, and the MIC drugs wre CIP,NOR, LVF, GAT. The result shows that the tolerance of DH5α with rasistance plasmid forquinolone drugs has a rise from sensitive to intermediary; the MICs of CIP and NOR, LVFand GAT increase by2--32times, also. The result proves that this plasmid with qnr shows lowlevel resisitance to quinolone drugs.