【摘要】 目的研究本地区质粒介导的喹诺酮类耐药基因aac(6’)-Ib-cr和qnr在肺炎克雷伯菌中的发生率及接合子对环丙沙星和左氧氟沙星不同耐药水平的发生机制。方法筛选2007年7月～2008年12月本院临床分离的产超广谱β-内酰胺酶的肺炎克雷伯菌共57株,采用PCR法检测qnrA、qnrB、qnrS和aac(6’)-Ib阳性菌株并对部分菌株进行测序。以大肠埃希菌J53为受体菌,通过接合试验从aac(6’)-Ib-cr和(或)qnr阳性菌株中获得接合子,采用E-test方法测定菌株的药敏情况。结果所分离的57株肺炎克雷伯菌中aac(6’)-Ib基因阳性菌12株,经测序全部为aac(6’)-Ib-cr基因,阳性检出率为21.1%;qnr基因阳性菌25株(43.9%),其中3株(5.3%)含qnrA基因,21株(36.8%)含qnrB基因,20株(35.1%)含qnrS基因;aac(6’)-Ib-cr、qnrA、qnrB和qnrS均阳性菌共3株(5.3%),qnrB和qnrS均阳性菌共13株(22.8%)。本研究中共有14株菌株接合试验获得成功,环丙沙星和左氧氟沙星对接合子的最低抑菌浓度(MIC)范围分别为0.25～0.5μg/ml和0.25～1μg/ml;接合子与受体菌的MIC值比较结果显示,环丙沙星耐药性提高了31～63倍,左氧氟沙星耐药性提高了17～63倍。结论本地区产超广谱β-内酰胺酶的肺炎克雷伯菌质粒介导的喹诺酮类耐药基因aac(6’)-Ib-cr和qnr携带率很高,部分菌株的喹诺酮类抗菌药物MIC值升高与喹诺酮类耐药基因aac(6’)-Ib-cr和(或)qnr有关。更多还原

【Abstract】 Objective To observe the incidence of plasmid-mediated quinolone resistance gene aac ( 6’) -Ib-cr and qnr in Klebsiella pneumoniae and to study on the mechanism of integron mediated different risistance levels to ciprofloxacin and levofloxacin. Methods Total of 57 strains of Klebsiella pneumoniae producing extended spectrum β-lactam enzyme were selected from our hospital during July 2007 to December 2008. The qnrA,qnrB,qnrS and aac ( 6’) -Ib-positive strains were detected by PCR and some of the strains were sequenced. Zygote were abtained from aac ( 6’) -Ib-cr and ( or) qnr positive strains by conjugation test,with Escherichia coli J53 as the recipient strain. Susceptibility of strains were determined by E-test method. Results Among the 57 strains of Klebsiella pneumoniae,12 strains were aac ( 6’) -Ib gene positive which accouted for 21. 1% and were all aac ( 6’) -Ib-cr gene detected by sequence analysis. There were 25 strains with qnr gene positive which accouted for 43. 9% ,3 strains of which contained qnrA gene ( 5. 3% ) , 21 strains contained qnrB gene ( 36. 8% ) ,20 strains contained qnrS gene ( 35. 1% ) . Total of 3 strains ( 5. 3%) were detected containing aac ( 6’) -Ib-cr,qnrA qnrB and qnrS,13 strains ( 22. 8%) were both qnrB and qnrS positive. Conjugation test were successful in 14 strains. The transconjugant showed 31-63 fold and 17-63 fold increased in the MICs of ciprofloxacin and levofloxacin,respectively,compared with the recipient. Conclusions There were high carrier rate of plasmid mediated quinolone resistance gene aac ( 6’) -Ib-cr and qnr of producing extended spectrum β-lactam enzyme Klebsiella pneumoniae in this region. The quinolone resistance gene aac ( 6 ’) -Ib-cr and ( or) qnr may contribute to the increased MICs of quinolone antibacterial drugs in some strains.更多还原