耐亚胺培南铜绿假单胞菌耐药特征及其耐药机制的研究

Antimicrobial Resistance Characteristics and Mechanism of Imipenem-resistant Pseudomonas aeruginosa

目的分析临床分离耐亚胺培南铜绿假单胞菌对常用抗菌药物的耐药特征及其对亚胺培南耐药机制。方法应用BD Phoenix100全自动微生物分析仪进行细菌鉴定和药物敏感试验,头孢哌酮/舒巴坦采用K-B法;应用聚合酶链反应（PCR）方法检测碳青酶烯酶相关基因（IMP、VIM、GIM、SPM、OXA、GES）、膜微孔蛋白基因oprD2,采用Etest试验观察氰氯苯腙（CCCP）对亚胺培南最低抑菌浓度（MIC）的影响,以研究细胞内主动外排机制。结果耐亚胺培南铜绿假单胞菌除对阿米卡星100%敏感外,对哌拉西林、哌拉西林/他唑巴坦敏感率为48.0%~54.0%,对三代、四代头孢菌素、氨曲南、喹诺酮类等抗菌药物抗菌活性差,敏感率为3.0%~29.0%;对美罗培南29.0%敏感,对氨苄西林/舒巴坦、氯霉素、四环素、复方新诺明全部耐药;检测到IMP阳性率17.6%,oprD2阳性率2.9%,其余耐药基因未检测到;当CCCP存在时,亚胺培南的MIC值下降4个浓度梯度,提示存在主动外排机制的菌株占11.8%。结论耐亚胺培南铜绿假单胞菌除阿米卡星外,对其他常用抗菌药物耐药严重;产IMP型金属β-内酰胺酶、细胞内主动外排机制以及膜微孔蛋白基因oprD2缺失,是铜绿假单胞菌对亚胺培南耐药的原因,但膜微孔蛋白基因oprD2缺失,不是铜绿假单胞对亚胺培南耐药的主要机制。

OBJECTIVE To investigate the antimicrobial resistance characteristics of Pseudomonas aeruginosa and the mechanisms of imipenem-resistance from producing carbapenemase, lacking outer membrane protein and active efflux pump system. METHODS Thirty four strains from patients from Jan to Dec 2005 were identified and drug susceptibility test was performed by BD Phoenix100 automatic microbial analysis system, cefoperazone/sulbactam detection was performed by K-B method. Carbapenemases,including IMP, VIM, GIM, SPM, GES, OXA and outer membrane protein oprD2 genes were detected by PCR method. Etest and carbonyl cyanide m-chlorophenylhydrazone（CCCP） were used to study the affection on the minimal inhibitory concentrations（MIC） of imipenem. RESULTS Imipenem-resistant P. aeruginosa was all susceptible to amikacin,near half （48-54%） was susceptible to piperacillin and pipercillin/tazobactam, respectively, only 3-29% were susceptible to the other cephalosporins, aztreonam and quinolones. There were 29% of P. aeruginosa susceptible to meropenem and all resistant to amoxicillin/clavulanate, chloramphenicol, tetracycline and trimethoprim/sulfamethoxazole. The positive rate of IMP and oprD2 genes were 17. 6% and 2. 9% respectively, while VIM, GIM, SPM, OXA, and GES genes were not detected. MIC to imipenem affected by CCCP was 11.8% in tested P. aeruglnosa. CONCLUSIONS The resistance of P. aeruglnosa to imipenem is a serious issue. The resistant P. aeruginosa to imipenem may be due to production of IMP metallo-β-1actamases, active efflux pump system or the loss of outer membrane protein oprD2, but lacking of oprD2 gene is not the main reason.