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目的 研究肺炎克雷伯菌对碳青霉烯类抗生素耐药的分子机制.方法 采用浓度梯度法(E-test)测定细菌对各种抗菌药物的最低抑菌浓度(MIC),聚合酶链反应(PCR)检测23种β-内酰胺酶基冈和2种膜孔蛋白基因,并对扩增产物进行基因测序.结果 5株肺炎克雷伯菌对哌拉西林、哌拉西林/他唑巴坦、阿莫西林/克拉维酸、头孢哌酮、头孢噻肟、头孢吡肟和氨曲南的MIC值均≥128 μg/mL,而对亚胺培南和美罗培南的MIC值均≥32 μg/mL.5株肺炎克雷伯菌均携带blaTEM-1和blaDHA-1基因.Kp01和Kp03同时出现ompK35和ompK36基因缺失.Kp02、Kp04、Kp05的ompK36出现碱基插入,Kp02、Kp05的ompK35碱基缺失.与GenBank(G0945384)比较,Kp04的ompK35基因发生第465位G→C和466位T→C突变,致Gln 155 His、Tyr 156 His氨基酸替换,可能为新的亚型.结论 β-内酰胺酶的产生合并OmpK36或OmpK35膜孔蛋白基因的缺失可引起肺炎克雷伯菌对碳青霉烯类抗生素耐药.

Objective To investigate the molecular mechanism of Klebsiella pneumoniae resistant to carbapenem. Methods The minimal inhibitory concentrations ( MICs) of the antimicrobial agents were determined by E-test. The 23 β-lactamase genes and 2 porin genes were amplified by polymerase chain reaction (PCR) , then the products were purified and their sequences were analyzed. Results The MICs of piperacillin, piperacillin/sulbactam, amoxicillin/clavulanic acid, cefoperazone/sulbactam, cefotaxime, cefepime and aztreonam to 5 strains of Klebsiella pneumoniae were all higher than 128 μg/mL, and those of imipenem or meropenem were higher than 32 μg/mL. All isolates carried blaTEM-1 and blaDHA-1 genes. Deletion of ompK35 and ompK36 were observed in Kp01 and Kp03, and the deletion of ompK35 was also observed in Kp02 and Kp05. Base insertion of ompK36 occurred in Kp02, Kp04 and Kp05. Compared with GenBank (GU945384) , ompK35 gene mutations of G→C at base 465 and T → C at base 466 in Kp04 lead to Gln to His substitution at position 155 and Tyr to its substitution at position 156, and it might be a new subtype. Conclusion The production of DHA-1 β-lactamase combined with the loss of OmpK36 or OmpK35 in porin genes may contribute to high-level carbapenem resistance in Klebsiella pneumoniae.