1株携带多种喹诺酮类药物耐药机制肺炎克雷伯菌的发现

Discovery of a Klebsiella pneumoniae Isolate Which Carried Multiple Quinolones-resistant Mechanisms

目的研究肺炎克雷伯菌(KPN)烧伤分离株的喹诺酮类耐药机制。方法测定1株分离自烧伤科患者血液的肺炎克雷伯菌对3种喹诺酮类药物的敏感性,采用PCR方法进行6种喹诺酮类耐药基因[aac(6′)-Ⅰb、qnrA、qnrB、qnrS、qepA和gyrA]检测,并对aac(6′)-Ⅰb和gyrA PCR阳性产物进行基因测序并作BLASTx比对分析。结果该菌株对诺氟沙星和环丙沙星耐药,对左氧氟沙星敏感;PCR检测发现该菌株同时携带qnrB、qnrS及aac(6′)-Ⅰb,对aac(6′)-Ⅰb基因测序证实为aac(6′)-Ⅰb-cr突变体,对gyrA基因测序证实其83位丝氨酸(S)被异亮氨酸(I)所替代,并有65位丝氨酸(S)发生同义突变,作为新亚型已登录美国NCBI基因库(登录号为GQ422758)。结论首次发现一同时携带qnrB、qnrS及aac(6′)-Ⅰb-cr共3种质粒介导的喹诺酮类耐药基因肺炎克雷伯菌烧伤分离株,同时其gyrA基因66、83位氨基酸均有突变,为一新亚型;这对临床上预防控制多药耐药KPN在烧伤科的流行提出了更高的要求。

OBJECTIVE The quinolones-resistant mechanisms carried by a strain of Klebsiella pneumoniae isolated from a burned patient were studied.METHODS The susceptibility of a strain of K.pneumoniae isolated from the blood of a burned patient to three quinolones antibiotics were detected.Subsequently,six quinolones-resistant genes（aac（6′）-Ⅰb,qnrA,qnrB,qnrS,qepA and gyrA） were detected by PCR and genes of positive products of aac（6′）-Ⅰb and gyrA were then sequenced and Blast analyzed.RESULTS The studied strain was resistant to norfloxacin,ciprofloxacin and sensitive to levofloxacin.Three plasmid-mediated genes of qnrB,qnrS and aac（6′）-Ⅰb were found in this strain and aac（6′）-Ⅰb was confirmed to be variant by sequence analyzed.Simultaneously,gyrA mutations were identified with Ser-83→Ile and synonymous mutation of DNA sequences in No.66 of the amino acid coden.This gene has been confirmed to be a novel subtype of gyrA gene（GenBank accession number,GQ422758）.CONCLUSION A strain of K.pneumoniae isolated from a burned patient carrying three plasmid-mediated quinolones-resistant genes,qnrB,qnrS and aac（6′）-Ⅰb-cr,was first discovered and its gyrA genes was a novel subtype for its mutation of DNA sequences in No.66 and No.83 of the amino acid coden.It will be more difficult to prevent and control the prevalence of multidrug-resistant K.pneumoniae.