阴沟肠杆菌对碳青霉烯酶类抗生素耐药机制的研究

Mechanism of drug resistance of Enterobacter cloacae to carbapenem

目的:研究碳青霉烯类高水平耐药的阴沟肠杆菌临床分离株对碳青霉烯类耐药主要机制。方法:筛选对碳青霉烯类高水平耐药的阴沟肠杆菌临床分离株21株,同时采用微量肉汤稀释法测定这些细菌对不同抗生素的最小抑菌浓度(minimal inhibitory concentration,MIC),改良Hodge实验、Carba NP试验检测是否产碳青霉烯酶;PCR检测碳青霉烯酶类型(bla KPC、bla IMP、bla NDM、bla VIM、bla IMI、bla SPM、bla NDMOXA-23、bla NDMOXA-24、bla NDMOXA-48、bla NDMOXA-58)。结果:药敏试验显示碳青霉烯类高水平耐药阴沟肠杆菌具有多重耐药性。改良Hodge实验、Carba NP试验阳性率分别为61.9%(13/21)、90.5%(19/21);PCR扩增碳青霉烯酶基因,21株试验阴沟肠杆菌19株有扩增产物,IMP、KPC、NDM阳性率分别为23.8%(5/21)、9.5%(2/21)、61.9%(13/21),其中一株阴沟肠杆菌既产IMP又产NDM。结论:产碳青霉烯酶是临床分离碳青霉烯类高水平耐药阴沟肠杆菌的主要耐药机制,应当引起院感控制人员的高度重视。

Objective：To investigate the mechanism of clincal isolates of carbopenem-resistant Enterobacter cloacae. Methods：Antimicrobial susceptibility test was done on 21 strains of Enterobacter cloacae by Kirby-Bauer method. The minimal inhibitive concentrations（MICs）of these antimicrobial agents were determined by microdosis broth dilution method. A modified Hodge test and Carba NP test were used to detect the presence of carbapenemase. The genotype of KPC,IMP,NDM,VIM,IMI,SPM,OXA-23,OXA-24,OXA-48 and OXA-58 was tested by polymerase chain reaction（PCR）. Results：Clinical isolates of carbapenem-resistant Enterobacter cloacae were multi-drug resistance. The positive rate of modified Hodge test and Carba NP test were 61.9%（13/21）,90.5%（19/21）,respectively. Carbapenemase genes were positive in 19/21 strains of Enterobacter cloacae by PCR. The positive rate of IMP,KPC and NDM were 23.8%（5/21）,9.5%（2/21）and 61.9%（13/21）,respectively,in which one strain was both IMP and NDM positive.Conclusion：Production of carbapenemases is the main mechanism of carbapenem-resistant Enterobacter cloacae,which should arouse the attention of stalf in hospital infection-control department.