Objective To investigate the phenotypic characteristics and molecular mechanisms of clinically isolated quinolone resistant Escherichia coli.Methods Quinolone resistant strains of Escherichia coli were screened from clinical isolates through drug sensitivity testing.After multilocus sequence typing(MLST),PCR detection and gene sequencing were used to analyze the quinolone-resistance determining regions(QRDR)and plasmid-mediated quinolone resistance(PMQR).Results The collected 53 strains of Escherichia coli showed intermediate resistance or resistance phenotype to levofloxacin.They were divided into 21 types by MLST,and ST53 and ST43 were predominant.Compared with sensitive strains,QRDR sequencing results showed that the main mutations were S83L and D87N of gene GyrA and S80I of gene ParC,accounting for 94.33%,79.25%and 79.25%,respectively.Both ST53 and ST43 showed the presence of these three site mutations.PMQR detection results showed that 32.08%of the strains detected PMQR genes of aac(6)-Ib-cr,qnrB and qnrS.In addition,the positive rate of the disinfectant resistance gene qacE △ 1 accounted for 62.26%.Conclusion The resistance mechanism of quinolone resistant Escherichia coli is mainly related to three site mutations in QRDR region.At the same time,monitoring of plasmid mediated resistance gene transmission should be enhanced.
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