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目的了解质粒介导喹诺酮耐药基因qnr在肺炎克雷伯杆菌中的流行情况并探讨其相关耐药机制。方法纸片法和E-test法检测肺炎克雷伯杆菌对抗菌药物的敏感性;多重PCR方法检测菌株中qnr的携带情况;接合实验证实qnr的可转移性;肠道细菌基因间重复序列PCR(ERIC-PCR)分型检测qnr阳性菌株的同源性;变性高效液相色谱技术(DHPLC)检测qnr阳性菌株染色体旋转酶GyrA和拓扑异构酶ParC变异位点。结果 2006年首都医科大学附属北京朝阳医院临床分离的160株肺炎克雷伯杆菌中检出48株qnr阳性菌株,分别为1株qnrA阳性菌,21株qnrB阳性菌,22株qnrS阳性菌,4株同时携带qnrB和qnrS。25株qnrB阳性菌和7株qnrS阳性菌接合实验成功。同源性分析未发现qnr基因在院内有暴发流行。检测到GyrA亚基存在4种氨基酸突变类型,ParC亚基存在2种氨基酸突变类型。结论本研究分离的肺炎克雷伯杆菌中qnrB和qnrS为流行亚型。qnr基因在不同菌株中可水平转移,与编码GyrA和ParC氨基酸位点突变同时存在时可导致高水平耐药。
Objective To investigate the prevalence of qnr, a plasmid-mediated quinolone resistance gene, in Klebsiella pneumoniae and to explore its related mechanisms of resistance. Methods The susceptibility of Klebsiella pneumoniae to antibacterials was tested by disk method and E-test. The multiplex PCR was used to detect the qnr in the strains. The conjugation experiments confirmed the transferability of qnr. (ERIC-PCR) was used to detect the homology of qnr positive strains. The chromosome gyrase GyrA and topoisomerase ParC mutation sites of qnr positive strains were detected by denaturing high performance liquid chromatography (DHPLC). Results A total of 48 strains of qnr were detected in 160 strains of Klebsiella pneumoniae isolated from Beijing Chaoyang Hospital affiliated to Capital Medical University in 2006. They were 1 strains of qnrA, 21 strains of qnrB, 22 strains of qnrS, 4 Strains carry both qnrB and qnrS. 25 strains of qnrB positive bacteria and 7 strains of qnrS positive bacteria were successfully combined. Homology analysis found no outbreak in the hospital qnr gene epidemic. There are four kinds of amino acid mutations in GyrA subunit. There are two kinds of amino acid mutations in ParC subunit. Conclusion qnrB and qnrS of Klebsiella pneumonia isolated in this study are epidemic subtypes. The qnr gene can be horizontally translocated in different strains and can lead to high levels of resistance when present together with mutations in the amino acid sequences encoding GyrA and ParC.