多药耐药鲍氏不动杆菌对喹诺酮类耐药相关基因研究

Quinolones resistance genes in multidrug-resistant Acinetobacter baumannii

目的了解多药耐药鲍氏不动杆菌对喹诺酮类耐药相关基因的存在和变化状况,为临床合理用药提供参考。方法收集医院2011年1-12月住院患者痰液标本中分离的20株多药耐药鲍氏不动杆菌,采用聚合酶链反应(PCR)及序列分析的方法,分析喹诺酮类药物作用靶位拓普异构酶Ⅱ编码基因A亚单位基因gyrA以及由可移动遗传元件介导的喹诺酮类耐药相关基因(qnrA、qnrB、qnrS、qepA、aac(6′)-Ⅰb-cr)有无变异。结果 20株鲍氏不动杆菌除13、14号菌株对环丙沙星和左氧氟沙星敏感外,其余均为耐药或中介,其中对哌拉西林、头孢他啶、头孢曲松、头孢吡肟和亚胺培南全部耐药,对氨基糖苷类药物、氟喹诺酮类药物和磺胺甲噁唑/甲氧苄啶3类药物耐药性均>90.0%;多药耐药鲍氏不动杆菌除13、14号株外,其余18株gyrA基因喹诺酮耐药决定区第83位密码子TCA→TTA均有义突变(氨基酸序列Ser→Leu),20株菌株第87位密码子GAA均无变异;可移动遗传元件介导的喹诺酮类耐药相关基因(qnrA、qnrB、qnrS、qepA、aac(6′)-Ⅰb-cr)均未检测出。结论鲍氏不动杆菌对喹诺酮类药物耐药可能与gyrA基因突变有关。

OBJECTIVE To investigate the presence and change of quinolone resistance genes in multidrug-resistant Acinetobacter baumannii （A. baumannii） so as to provide guidance for the reasonable use of antibiotics. METHODS A total of 20 strains of multidrug-resistant A. baumannii, which were isolated from the sputum specimens obtained from the patients who were hospitalized from Jan to Dec 2012, were enrolled in the study, then the polymerase chain reaction （PCR） and DNA sequencing were employed to analyze the quinolone target topoisomerase II encoding A subunit gene gyrA and to determine whether or not the variants of mobile genetic elements-mediated quinolones resistance genes （qnrA, qnrB, qnrS, qepA, aac（6＇） - I ＆cr） presented. RESULTS No. 13 and No. 14 strain were susceptible to ciprofloxacin and levofloxacin, the rest of thes trains were resistant or intermediate, all of which were resistant to piperacillin, ceftazidime, ceftriaxone, cefepime, and imipenem; the drug resistance rates to aminoglycosides, fluoroquinolones, and sulfamethoxazole-trimethoprim were more than 90. 0%. All the mutidrug-resistant A. baumannii isolates except for the No. 13 and No. 14 had the mutation of 83th codon TCA→TTA of quinolone resistance determining region （amino acid Ser →Leu）of gyra; none of the 20 strains had the mutation of 87th codon GAA. The quinolones resistance genes （qnrA, qnrB, qnrS, qepA, aac（6＇） - Ib-cr） mediated by the mobile genetic elements were not detected. CONCLUSION The quinolones resistance of the A. baumannii isolates may be associated with the mutation of gyrA gene.