多药耐药鲍曼不动杆菌OXA酶检测及医院内感染的分子机制

Detection of OXA carbapenemases and molecular mechanism in nosocomial outbreak caused by multi-drug resistant Acinetobacter baumannii strains

目的了解本院多药耐药鲍曼不动杆菌产OXA酶情况、基因同源性及传播机制,为临床防治提供依据。方法采用琼脂稀释法检测鲍曼不动杆菌的最低抑菌浓度(MIC),改良Hodge试验检测碳青霉烯酶,PCR进行OXA酶的基因分型,并对PCR产物进行测序;ERIC-PCR分析鲍曼不动杆菌基因同源性,转移接合试验进行基因定位。结果 45株菌耐药情况较严重;在42株耐碳青霉烯类鲍曼不动杆菌中,表型和基因型检测显示产OXA酶34株;ISAba1-blaOXA-23阳性39株,blaOXA-23阳性3株;42株菌blaOXA-23均位于染色体。blaOXA-58阳性3株,2株blaOXA-58位于染色体,1株blaOXA-58位于质粒上。42株blaOXA-23阳性鲍曼不动杆菌属于6种分型(A、B、C、D、E、F),其中A型34株,B型4株,A、B两型间具有亲缘关系。结论本组多药耐药鲍曼不动杆菌对碳青霉烯类耐药主要是产OXA-23酶,携带blaOXA-23鲍曼不动杆菌存在医院内克隆传播。

Objective To investigate the prevalence of OXA carbapenemases,gene homology and transmission mechanism of multidrug resistant Acinetobacter baumannii strains in this hospital,identify their characteristics of drug resistance patterns,and provide the evidence for clinical prevention and treatment.Methods Minimum inhibitory concentrations （MIC） of Acinetobacter baumannii strains were determined by agar dilution method.Carbapenemase was detected by modified Hodge test.The genotypes of OXA carbapenemase were detected by PCR and DNA sequencing.Genetic homology of Acinetobacter baumannii was analyzed by enterbacterial repetitive intergenic consensus （ERIC）-PCR and Acinetobacter baumannii gene was localized by transfer bonding technique.Results Forty-five isolates were identified as seriously drug-resistant.Among the 42 carbapenem-resistant Acinetobacter baumannii 34 were found to produce OXA carbapenemase by detection of phenotype and genotype,39 strains was positive ISAba1-blaOXA-23,3 strains was positive blaOXA-23.In all of the 42 strains blaOXA-23 was located in bacteria1 chromosomes.Among the 3 strains with positive blaOXA-58,blaOXA-58 gene of 2 strains located in bacteria1 chromosomes while the other 1 strain located in plasmid.The 42 Acinetobacter baumannii strains with blaOXA-23 belonged to 6 types （A-F） respectively.Thirty-four of them belonged to type A,four belonged to type B,and the 38 strains had genetic relationship with each other.Conclusion Production of OXA-23 carbapenemase-produced strains of Acinetobacter baumannii was the main mechanism for the multi-drug resistance for carbapenem in this study.The nosocomial outbreak was caused by clonal epidemic transmission of Acinetobacter baumannii strain carried blaOXA-23.