临床分离大肠埃希菌质粒介导喹诺酮耐药基因和β内酰胺酶基因检测

Survey on the genes conferring plasmid-mediated quinolone resistance and those encoding β-lactamases in Escherichia coli isolates

目的探讨大肠埃希菌临床分离株质粒介导喹诺酮耐药(PMQR)基因的流行情况,及其与β内酰胺酶基因相关性。方法收集2013年7-12月福建医科大学附属协和医院临床分离的对左氧氟沙星和/或环丙沙星耐药的大肠埃希菌200株,采用PCR检测qnrA、qnrB、qnrC、qnrD、qnrS、aac(6')-Ib-cr、qepA和oqxAB基因,对PMQR基因阳性菌株扩增常见β内酰胺酶基因;采用琼脂稀释法对PMQR基因阳性菌株进行药敏试验,以及PCR法对菌株进行系统发育分型;利用肠杆菌基因重复一致序列分析(ERIC-PCR)进行菌株同源性分析。结果 PCR扩增结果显示实验菌株PMQR阳性率为29.0%(58/200)。其中qnr阳性率为5.5%(11/200),aac(6')-Ib-cr阳性率为20.5%(41/200),oqx AB阳性率为8.0%(16/200),qepA阳性率为0.5%(1/200)。58株PMQR基因阳性菌株中CTX-M-1组32株(55.2%)、CTX-M-9组17株(29.3%)和TEM型1株(1.7%),未检出SHV型β内酰胺酶基因。PMQR阳性菌呈现多重耐药现象;系统发育分型结果显示A型有21株(36.2%),D型17株(29.3%),B2型11株(19.0%),B1型9株(15.5%)。ERIC-PCR显示PMQR大肠埃希菌可分为50个不同的型别,其中1株未能分型。结论该院大肠埃希菌中PMQR基因以aac(6')-Ib-cr、qnr和oqxAB为主,且与β内酰胺酶耐药基因高度相关;此外PMQR菌株以非克隆播散方式在该院中流行。

Objective To examine the prevalence of plasmid mediated quinolone resistance （PMQR） genes and their correlation with the genes encoding β-lactamases in E. coli isolates. Methods A total of 200 levofloxacin- and/or ciprofloxacin-resistant E. coli isolates were collected from Fujian Medical University Union Hospital during the period from July to December 2013. PCR method was used to screen these E. coli isolates for the presence of qnrA, qnrB, qnrC, qnrD, qnrS, aac（6＇）-lb-cr, qepA, oqxAB genes, and the blarEM, blasnv and blaCTX-M genes in the PMQR positive strains. Agar dilution method was utilized to measure the antimicrobial susceptibility of PMQR-positive strains. Phylogenetic analysis was conducted by triplex PCR. Enterobacterial repetitive intergenic consensus-polymerase chain reaction （ERIC-PCR） was used to evaluate the genetic similarity between the PMOR-Dositive isolates.Results Of the 200 clinical isolates of E. coli, 58 （29.0%） were PMQR-positive. And qnr, aac（6＇）-Ib-cr, oqxAB, and qepA genes were positive in 11 （5.5%）, 41 （20.5%）, 16 （8.0%）, 1 （0.5%） strains, respectively. The genes encoding CTX-M-1, CTX-M-9 and TEM type enzymes was positive in 32 （55.2%）, 17 （29.3%）, and 1 （1.7%） of the PMQR-positive strains, respectively. The blasHv gene was not identified in any isolate. PMQR-positive strains were multi-drug resistant. Phylogenetic analysis indicated that 21 （36.2%）, 17 （29.3%）, 11 （19.0%）, and9 （15.5%） of the PMQR-positive strains belonged to group A, group D, group B2 and group B 1, respectively. ERIC-PCR suggested the PMQR-positive isolates belonged to 50 different types. Only one strain was non-typeable. Conclusions Most of the PMQR- related genes in E. coli are aac（6＇）-Ib-cr, qnr, and oqxAB in our hospital, which are highly relevant to β-lactamase genes. PMQR- positive strains may spread by way of non-clonal dissemination in our hospital.