一种新的质粒介导的IMI-1型碳青霉烯酶

目的　确立亚胺培南耐药阴沟肠杆菌对亚胺培南的耐药机制。方法　采用Etest测定抗菌药物最低抑菌浓度 (MIC) ,通过等电点聚焦电泳 (IEF)、三维试验、接合试验、Southern杂交、聚合酶链反应 (PCR)、克隆测序对酶的活性及编码基因进行研究。结果　阴沟肠杆菌产碳青霉烯酶 ,等电点为 8.1。该酶能被克拉维酸抑制 ,不被氯唑西林、EDTA抑制 ,存在 2f类酶的某些特性 ,其耐药基因位于 80kb左右的质粒上。克隆测序显示与染色体介导的IMI 1有 99%的同源性。结论　阴沟肠杆菌对亚胺培南耐药是由一种新的质粒介导的与染色体介导的IMI 1类似的碳青霉烯酶所致。

A novel plasmid-mediated IMI-1-like carbapenemase

Objective To investigate the resistant mechanism of imipenem-resistant Enterobacter cloacae. Methods The minimal inhibitive concentration (MIC) was detected by E test. Isoelectric focusing electrophoresis(IEF), three dimensional test, conjugation experiment, Southern blot, polymerase chain reaction(PCR), cloning and sequencing methods were applied for analyzing the enzyme activity and the encoding gene. Results The carbapenemase produced by Enterobacter cloacae had the bands with pIs 8.1. The carbapenemase had some characteristics of Class 2f. The activity of hydrolysising imipenem was inhibited by clavulanic acid, but not inhibited by cloxacillion and EDTA. The imipemen-resistant gene was located on a about 80kb plasmid and the amino acid sequence have 99% of homology with chromosome-mediated IMI-1. Conclusion The E. cloacae resistant to imipenem was explained by a novel plasmid-mediated IMI-1-like carbapenemase.