肺炎克雷伯菌产KPC酶合并膜孔蛋白OmpK36缺失对头孢他啶/阿维巴坦耐药的分子机制研究

Molecular mechanism of resistance of Klebsiella pneumoniae to ceftazidime/avibactam due to combination of KPC enzyme and the loss of OmpK36 porin

目的研究产KPC酶肺炎克雷伯菌(Klebsiella pneumoniae,Kp)对头孢他啶/阿维巴坦耐药的分子机制。方法临床分离2株对头孢他啶/阿维巴坦耐药的产KPC酶Kp C9和C14,利用胶体金法进行碳青霉烯酶型检测,基质辅助激光解吸飞行时间质谱(MALDI-TOF MS)进行同源性分析,MIC法进行药物最低抑菌浓度检测,聚丙烯酰胺凝胶电泳(SDS-PAGE)及基因测序检测外膜蛋白表达及基因突变,羰基氰化物间氯苯腙(CCCP)抑制试验检测主动外排机制。结果产KPC酶Kp C9和C14同其他产KPC酶Kp同源性较低,对头孢他啶/阿维巴坦的MIC分别为16和32μg/mL,外膜蛋白SDS-PAGE显示Kp C9和C14均有OmpK36的缺失,外膜蛋白基因序列分析显示Kp C9和C14的OmpK36基因序列均存在个别位点的突变、缺失,CCCP抑制试验显示CCCP不能提高Kp C9和C14对头孢他啶/阿维巴坦的敏感性。结论KPC酶合并膜孔蛋白OmpK36缺失可引起Kp对头孢他啶/阿维巴坦耐药。

Objective To study the molecular mechanism of resistance of Klebsiella pneumoniae(KP)producing KPC enzyme against ceftazidime/avibactam.Methods Kp C9 and C14 which producing KPC enzyme resistant to ceftazidime/avibactam were clinically isolated,and the carbapenemase type was detected by the colloidal gold method.Homology analysis was carried with matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF MS).The minimum inhibitory concentration(MIC)method was used to perform drug resistant tests.Outer membrane protein expressions were examined by SDS-PAGE.Gene mutations were detected by gene sequencing.Inhibition assays were performed by carbonyl cyanide m-chlorophenylhydrazone(CCCP)to detect active efflux system.Results Kp C9 and C14 producing KPC enzyme have low homology with other Kp producing KPC enzymes.MIC of Kp C9 and C14 to ceftazidime/avibactam was 16~32μg/mL,respectively.SDS-PAGE showed that both Kp C9 and C14 had the loss of OmpK36.The OmpK36 gene sequence of Kp C9 and C14 contained a few point mutations and deletions at individual sites.The MIC of ceftazidime/avibactam did not change in the presence of CCCP.Conclusion Ceftazidime/avibactam resistance in Kp C9 and C14 isolates is attributable to the production of KPC enzyme combined with the loss of OmpK36 porin.