亚胺培南耐药鲍曼不动杆菌同源性及碳青霉烯酶研究

目的 明确我院临床分离亚胺培南耐药鲍曼不动杆菌的耐药性、同源性及碳青霉烯酶基因型。方法 收集我院2003年8月-2004年12月分离的95株亚胺培南耐药鲍曼不动杆菌。琼脂稀释法和E试验法测定15种抗菌药物的MIC值；脉冲场凝胶电泳（PFGE）分析菌株的同源性；PCR扩增及克隆测序分析碳青霉烯酶基因型；接合试验、质粒抽提及Southern杂交完成亚胺培南耐药基因定位。结果 95株鲍曼不动杆菌对氨苄西林-舒巴坦、头孢哌酮-舒巴坦两个含舒巴坦制剂耐药率分别为67．9％、30．2％，对多黏菌素E耐药率最低，为17％，对其他抗菌药物的耐药率均在90％以上。95株鲍曼不动杆菌分离自10个临床科室，均产OXA-23碳青霉烯酶，PFGE分型共分为6型，以A、B型为主。碱裂解法反复抽提均未得到质粒，多次接合试验未成功。Southern杂交证实A、B克隆的oxa-23耐药基因位于细菌染色体约220kb、200kb大小的ApaI酶切片段上。结论 产OXA-23型碳青霉烯酶鲍曼不动杆菌已成为我院医院感染的重要病原菌，在我院多个科室播散，且以A、B克隆为主。oxa-23耐药基因位于染色体上。

Study on the homology of imipenem-resistant Acinetobacter baumannii and the genotype of carbapenemase

Objective To characterize the antibiotic resistance,homology and carbapenemase genotypes of imipenem resistant Acinetobac1ter baumannii isolated from our hospital,and analyze the clonal relatedness of the test strains.Methods Ninety five strains of imipenem resistant A.baumannii were isolated from August 2003 to December 2004 in the First Affiliated Hospital, College of Medicine,Zhejiang University.The MICs of 16 antimicrobial agents against these strains were determined by agar dilution and E-test method.The homology of these isolates was analyzed by pulse-field gel electrophoresis(PFGE).The coding gene of carbapenemases was amplified.PCR products were purified,cloned and sequenced.Plasmid DNA was extracted and purified.Conjugation and Southern blot were performed to locate the position of oxa 23 gene.Results The resistance rates to ampicillin-sulbactam and cefoperazone sulhactam were 67.9% and 30.2%.Polymyxin E had the lowest resistance rate of 17%. The resistance rate to other antimicrobial agents was higher than 90%.The 95 strains,isolated from 10 clinical units,were classified into 6 clones.Clones A and B were predominant clones.All strains produced carbapenemases which were confirmed as OXA 23 by PCR and sequencing analysis.No plasmid was extracted and conjugation was not successful.Southern bolt showed that oxa-23 gene was located on Apal-digested chromosomal segments about 220 kb and 200 kb in Clones A and B,re spectively.Conclusions OXA 23-producing A.baumannii has become one of the most important multi-resistant pathogens in our hospital.Clones A and B have widely spread in our hospital.Oxa-23 gene is located on chromosomal DNA.