碳青霉烯类耐药鲍曼不动杆菌流行病学及碳青霉烯酶类型的研究

Investigation on epidemiology of carbapenem-resistant Acinetobacter baumannii and carbapenemases

目的 了解碳青霉烯类耐药鲍曼不动杆菌的耐药性、同源性及碳青霉烯酶类型。方法 收集本院碳青霉烯类耐药鲍曼不动杆菌 45株 ,浓度梯度法 (Etest)测定最低抑菌浓度 (MIC) ;采用脉冲场凝胶电泳 (PFGE)分析同源性 ;通过等电点聚焦电泳 (IEF)、三维试验、2 巯基丙酸抑制试验、聚合酶链反应 (PCR)、克隆测序等方法分析碳青霉烯酶类型。结果 45株细菌均为多重耐药株 ,仅对头孢哌酮 /舒巴坦、氨苄西林 /舒巴坦耐药率较低分别为 2 2 %和 6 5% ,敏感率分别为 63 0 %和43 5%。 45株菌株PFGE图谱分为A、B两型 ,A型是主要流行株 (44株 ) ,主要集中在重症监护病房(ICU )。B型 1株来自血液科病房。 45株菌中有 43株产碳青霉烯酶 ,其中 16号株 (PFGE为B型 )等电点有 6 6、7 2两个条带 ,pI 6 6为OXA 2 3 ,其余 42株 (A1～A4亚型 )pIs均有 6 4、7 0两个条带 ,均不被克拉维酸、氯唑西林及 2 巯基丙酸抑制 ,PCR方法也未能检出OXA 2 3、OXA 2 4系列的基因。结论 本院碳青霉烯类耐药鲍曼不动杆菌流行主要为医院感染所致 ,该流行株呈多重耐药 ,未发现金属酶 ,仅 1株产OXA型碳青霉烯酶 ,为OXA 2 3。

Objective This study was designed to investigate the resistance and homology of carbapenem-resistant Acinetobacter baumannii and typing of carbapenemases. Methods 45 strains of carbapenem-resistant A. baumannii collected from clinical setting were analyzed by pulsed-field gel electrophoresis (PFGE), E test was made to determine the minimal inhibitory concentrations(MIC) of these strains, and the carbapenemases produced by these strains were typed by isoelectric focusing (IEF) electrophoresis, three-dimensional test, 2-mercaptopropanoic acid inhibited assays, polymerase chain reaction (PCR), cloning and sequencing methods. Results The resistance rates to cefoperazone/sulbactam and ampicillin/sulbactam were 2 2% and 6 5%, while the susceptibility rates to them were 63 0% and 42 5% respectively. Forty-five strains were classified into Type A and B based on PFGE pattern. Most of type A strains were isolated from ICU. Only 1 strain isolated from hematology department belongs to Type B. Forty-three strains produced carbapenemases. One strain had 2 bands on IEF electrophoresis. The pIs of which were 6.6 and 7 2 respectively. The band with pI of 6 6 was OXA-23. The other 42 strains produced 2 β-lactamases bands with pIs of 6 4 and 7 0 that couldn′t be inhibited by clavulanic acid, cloxacillin or 2-mercaptopropanoic acid,OXA-23、OXA-24 type gene weren′t detected by PCR methods. Conclusion The prevalence of carbapenem-resistant A. baumannii in our hospital was due to nosocomial infection. The prevalent strains were multiresistant. Metallo-beta-lactamase was not detected in any isolate. Only 1 strain produced OXA- type carbapenemase (OXA-23).