大肠埃希菌和肺炎克雷伯菌中质粒介导的喹喏酮类耐药研究

Plasmid-Mediated Gene for Quinolone Resistance(qnr) Produced by Clinical Strains of E.coli and K.Pneumoniae

目的:研究国内11家医院分离大肠埃希菌(ECO)和肺炎克雷伯菌(KPN)中质粒介导的喹喏酮类耐药。方法:收集北京大学第三医院无重复临床分离产超广谱β-内酰胺酶(ESBL s)的ECO和KPN共84株,另10家医院相应菌株共155株,北京协和医院对头孢西丁不敏感的ECO和KPN共25株。采用琼脂稀释法测定抗生素最低抑菌浓度M IC;接合实验判断该基因位置和移动性;聚和酶链反应(PCR)及其产物测序确定基因型。结果:北医三院84株菌中1株KPN(编号24)阳性,ECO的发生率是0;余10家医院155株产ESBL s菌株中没有阳性结果;协和医院25个临床株中3株KPN(编号P 3、P 6、P 10)阳性。这4株菌只有P 6接合试验阳性,相应接合子qnr-PCR阳性。环丙沙星C IP对该菌的M IC是0.5μg/m l,对该接合子的M IC是1μg/m l,而对受体菌EC 600的M IC是0.125μg/m l。对24号标本和P 6标本及其接合子进行测序证实:二者的qnr↑序列和AY 878718(qnrA)100%同源,并且qnr基因的上游都有ORF 513存在。结论:北医三院和北京协和医院分类株中存在质粒介导的喹喏酮类耐药基因qnr,其他医院分离株本次研究中未发现该基因。

Objective：To investigate the plasmid-mediated gene for quinolone resistance（qnr ↑ ） produced by the clinical strains of E. coli and K. pneumoniae isolated in 11 hospital. Methods ：A total of 84 clinical nonrepetitive isolates of E. coli and K. pneumoniae producing ESBLs was collected from June 2003 to July 2004 ;A total of 155 strains from 10 hospitals of China;and 25 strains nonsusceptible to cefoxitin from PUMCH. The Minimal Inhibitary Concentrations （MICs） were determined by 2-fold agar dilution method ;Coniugation test was used to determine the location and the transmission of genes; the genes were determined by PCR and DNA sequencing. Results：One strain from PK3H,three strains from PUMCH and no strains from other source produced qnr gene. Only 1 train successively coniugated its qnr gene to the recipient strains. The sequence of the gene was equal to AY878718（qnrA）in the GeneBank of NCBI. Conclu- sion ：Our research discovers qnr gene in clinical KPN strains isolated from the PK3H and PUMCH,but does not discover that gene in ECO or in other hospitals.