耐碳青霉烯肺克雷伯菌和大肠埃希菌耐药机制研究

Study on resistant mechanism of carbapenem resistant Klebsiella pneumoniae and Escherichia coli

目的分析该院临床分离的可疑产碳青霉烯酶肺炎克雷伯菌和大肠埃希菌的耐药性与耐药机制。方法采用VITEK-2全自动细菌鉴定仪检测其对21种抗菌药物的药敏结果,采用改良Hodge试验进行碳青霉烯酶筛选,用聚合酶链反应检测碳青霉烯酶KPC基因、外膜孔道蛋白(OmpK35和OmpK36)编码基因、转座子tnpA、tnpU基因。结果 47株可疑产碳青霉烯酶肺炎克雷伯菌和大肠埃希菌对青霉素类、头孢菌素类、喹诺酮类抗菌药物的耐药率高达80%以上,对亚胺培南、美罗培南、丁胺卡那霉素耐药率为35%以下;耐亚胺培南菌株对头孢哌酮/舒巴坦、头孢美唑、头孢替坦、头孢吡肟、哌拉西林/他唑巴坦、庆大霉素、妥布霉素、美罗培南、厄他培南的耐药率明显高于敏感菌株,二者差异具有统计学意义(P<0.05);改良Hodge试验阳性6株,检出碳青霉烯酶KPC基因4株,符合率为66.67%,均为KPC-2型;膜孔蛋白OmpK35、OmpK36基因缺失率分别为38.30%、65.96%;转座子tnpA、tnpU检出率分别为4.25%和38.30%。结论产碳青霉烯酶并非菌株耐碳青霉烯类药物的主要原因,尚存在其他耐药机制。

Objective To investigate the drug resistance and the resistant mechanism of suspicious carbapenemases in Kiebsiella pneumoniae and Escherichia coli clinical isolates. Methods All bacteria were isolated from the First Affiliated Hosphal of Guang- zhou Medical College,and antimicrobial susceptibility was done by VITEK-2 automatic bacterium identifying and drug sensitivity analyzing systems. The screening of the carbapenemase was detected by the modified Hodge test,and the polymerase chain reaction （PCR） was carried out to amplify carbapenem hydrolyzing gene（KPC）, outer membrane protein genes （OmpK35 and OmpK36）, transposon tnpA and tnpU. Results Among 47 strains of suspicious carbapenemases in Klebsiella pneurnoniae and Eschcrichia co-li, the higher drug resistance rates to them were penicillins,cephalosporins and quinolones, which were more than 80%. l hc rtsist ance rates for imipenem,meropenem and amikacin were less than 35 %. In addition to the imipenem-resistant strains, the resistance rates to eefoperazone/sulbactam, cefmetazole, cefotetan, cefepime, piperacillin/tazobactam, gentamicin, tobramycin, meropcnem and ertapenem were significantly higher than the sensitive strains（P〈0.05）. 6 strains were positive in the modified Hodge test, whh 4 strains carried out KPC-2 gene, and the correspondence rate of 66. 67%. The absence rates of outer membrane protein genes （OmpK35 and OmpK36）were 38.30% and 65.96% ,respectively. The positive rates of transposition tnpA and tnpU accounted for 4.25% and 38.30%, respectively. Conclusion The emergence of carbapenemase is not the main reason of carbapenem resistance producers in bacteria,and there may be other resistant mechanisms to reduced susceptibility of earbapenems.