质粒介导的喹诺酮耐药基因在中国大陆尿液分离的大肠埃希菌中的广泛分布

目的分析中国大陆20家三甲医院尿来源大肠埃希菌的耐药特点并调查质粒介导的喹诺酮类耐药基因的分布情况和流行特点。方法收集卫生部全国耐药监测网2007年1月至2008年3月非重复298株尿液分离大肠埃希菌;琼脂稀释法测定其对20种抗菌药物的敏感性,多聚酶链反应和DNA测序分析qn-rA,qnrB,qnrS,aac(6’)-ib和qepA基因的流行性;接合实验分析质粒的转移性;Eric-PCR分析喹诺酮基因阳性菌株之间的遗传相关性;卡方检验用于分析耐药基因与氟喹诺酮耐药之间的相关性。结果 298株大肠埃希菌对20种抗菌药物耐药现象严重,其中对环丙沙星和左氧氟沙星有很高的耐药性,耐药率高达78.5%和74.2%。经基因比对分析,62株(20.8%)细菌携带aac(6’)-Ib基因;45株(15.1%)细菌携带喹诺酮耐药基因,1株(0.3%)检测出qnrA基因,3株(11.4%)检出qnrB基因,5株(1.7%)检出qnrS基因,25株(8.4%)确定为aac(6’)-Ib-cr基因,12株(4.7%)检出qepA基因;此外,有3株细菌分别发现aac(6’)-Ib-cr和qepA1基因aac(6’)-Ib-cr和qnrB1基因,qepA和qnrS1基因共存。45株喹诺酮基因阳性菌株之间具有很大的遗传差异,并且其中有16株细菌携带的基因具有可转移性。aac(6’)-Ib的流行性与细菌的环丙沙星和左氧氟沙星不敏感性相关(P<0.05);喹诺酮耐药基因的流行性与细菌的氟喹诺酮不敏感性相关(P<0.05)。结论尿液分离的大肠埃希菌耐药严重,质粒介导的喹诺酮耐药基因主要以aac(6’)-ib-cr为主,qepA1次之,这些潜在播散的喹诺酮耐药基因对于临床尿路感染的治疗有很大的挑战。

Broad distribution of plasmid mediated quinolone resistance genes among urinary Escherichia coli in mainland, China

Objective To investigate the resistance characterization and the prevalence of plasmid-mediated quinolone resistance(PMQR) determinants among the urinary Escherichia coli.isolates from 20 Chinese tertiary hospitals in the national wide.Methods Non-replicate 298 clinical strains were collected from the Ministry of Health National Antimicrobial Resistance Surveillance Net(Mohnarin) during the time period of January 2007 to March 2008.Susceptibility testing by agar serial dilution was implemented to analyze the resistant characterization;The prevalence of qnrA,qnrB,qnrC,qnrS,aac(6’)-ib,aac(6’)-ib-cr and qepA were confirmed by PCR and DNA sequencing.The transferability of the plasmids harboring PMQR genes were investigated by conjugation test.Enterobacterial Repetitive Intergenic Consensus-PCR(Eric-PCR) was carried out to analyze the clonal relatedness of PMQR genes positive isolates.Results Multiresistant bacteria were very common and a serious fluoroquinolone resistance were observed in the urinary E.coli isolates.Moreover,45 out of the 298 isolates(15.1%) were found to carry the PMQRs and a further 1(0.3%),3(11.5%),5(1.7%),25(8.4%) and 12(4.7%) of these isolates carried qnrA,qnrB,qnrS,aac(6’)-Ib-cr and qepA genes,repectively.An obvious genetic difference was observed among the 45 strains harboring PMQRs with 16 isolates carrying the transferable plasmids.There were associations between prevalence of aac(6′)-Ib with the non-susceptibility to ciprofloxacin and levofloxacin resistance(P<0.05).Associations between the prevalence of PMQRs genes with the non-susceptibility to fluoroquinolones were also observed(P<0.05).Conclusion The dominant PMQRs gene is aac(6′)-Ib-cr followed by qepA in the high fluoroquinolone resistance E.coli isolates from urine samples.Which alerts us to the potential rapid dissemination of quinolone resistance determinants and poses a serious challenge for the clinical therapy.