长沙地区临床分离碳青霉烯类耐药鲍曼不动杆菌的分子流行病学特征

Molecular epidemiological characteristics of clinically isolated carbapenem-resistant Acinetobacter baumannii in Changsha

目的:了解长沙地区临床分离鲍曼不动杆菌的耐药性,探讨碳青霉烯类抗生素耐药菌株的分子流行病学特征。方法:收集长沙地区10所综合性医院2010年3月至2010年12月间临床分离的非重复鲍曼不动杆菌株205株;采用K-B法检测药物敏感性,改良双纸片协同试验检测金属β-内酰胺酶(金属酶),改良Hodge试验筛查碳青霉烯酶;PCR扩增OXA-23,OXA-24,OXA-51,OXA-58及IMP-1和VIM-2型碳青霉烯酶基因,并进行测序分析。应用肠杆菌科基因间一致重复序列聚合酶链反应(enterobacterial repetitive intergenic consensus PCR,ERIC-PCR)对菌株进行DNA分型及同源性分析。结果:在监测的18种药物中,耐药率超过50%的达14种。其中哌拉西林耐药率最高(80.5%),头孢哌酮/舒巴坦耐药率最低(2.5%)。共筛选出耐碳青霉烯类药物鲍曼不动杆菌115株,其金属酶表型及基因检测均为阴性;改良Hodge试验阳性71株,其中64株OXA-23基因扩增阳性。115株菌株OXA-51均阳性,未检出OXA-24,OXA-58基因。115株菌株共分为7个ERIC基因型。其中A型19株,B型72株,为主要的流行克隆。结论:长沙地区临床分离鲍曼不动杆菌多重耐药十分严重;产OXA-23和OXA-51型碳青霉烯酶是鲍曼不动杆菌对碳青霉烯类药物耐药的重要机制,且碳青霉烯类耐药菌株存在克隆流行。

Objective： To survey antibiotic resistance of clinical isolates ofAcinetobacter baumannii in Changsha and to investigate molecular epidemiological characteristics of carbapenem-resistant Acinetobacter baumannii. Methods： A total of 205 non-duplicated, clinical isolates of Acinetabacter baumanniifrom 10 general hospitals in Changsha were collected from March 2010 to December 2010.The K-B disk diffusion method was applied for the drug-susceptibility test; a modified, double-disk synergy test was used to detect metallo-β-lactamase （MBL）, and a modified Hodge test was used for the screening of carbapenemase. PCR was used to amplify carbapenemase genes （including OXA-23, OXA-24, OXA-51, IMP-1, and VIM-2） and the positive products were sequenced. Enterobacterial repetitive intergenic consensus PCR （ERIC-PCR） was used for DNA typing and test of homology. Results： Of the 18 antibiotics tested, 14 had a high rate of resistance （〉 50% of the isolates tested）, with piperacillin the highest （80.5% of strains）, and cefoperazone/sulbactam the lowest （2.5%）. In total, 115 carbapenem-resistant Acinetobacter baumannii strains were confirmed, but their MBL phenotype and genes were all negative. Seventy-one positive strains were detected by the modified Hodge test, among which 64 strains were OXA-23-positive. All the 115 strains were positive for the amplification of the OXA-51 gene, and no strain was found which carried OXA-24 or OXA-58 gene. Seven genomic types were included in the 115 Acinetobacter baumannii. The major prevalence types were Type B （ 72 strains） and Type A （19 strains）. Conclusion： Multiple drug resistance of clinically isolated Acinetobacter baumannii is a serious problem in Changsha. Production of OXA-23 and OXA-51 carbapenemases is an important mechanism of resistance to carbapenem antibiotics, and there is prevalence of the same clones in these carbapenem-resistant strains.