Resistance Mechanism of Carbapenem-Resistant Enterobacteriaceae to Quinolones

To investigate the epidemics of plasmid-mediated quinolone resistance (PMQR) gene in carbapenem-resistant Enterobacteriaceae (CRE) and the resistance mechanism.

We collected CRE bacteria isolated clinically between December 2017 and December 2018 for identification and drug sensitivity testing using a VITEK2 Compact Analyzer. Furthermore, genes, including qnrA, qnrB, qnrS, qepA, and acc (6') Ib-cr, were determined through the polymerase chain reaction and sequencing. The hori-zontal transfer of PMQR gene was validated through the plasmid conjugational test.

Drug resistance rate of carbapenem-resistant Escherichia coli against quinolones was 100%, while the rate of carbapenem-resistant Klebsiella pneumoniae ranged from 15.56% to 33.33%. The detection rate of acc (6') Ib-cr was the highest (87.72%), followed by qnrB (77.19%) and qnrS (17.54%). Additionally, there were two bacteria carrying the qnrA gene (3.51%), but qepA gene was not isolated from the samples. In total, 84.21% of these bacteria carried 2 or 3 kinds of PMQR genes. Among 8 bacteria with successful plasmid conjugation, PMQR gene transfer was detected in all of them, but with no significant change in the minimum inhibitory concentration of quinolones.

CRE remain sensitive to quinolones in spite of the high detection rate of PMQR gene in this hospital.