摘要
目的调查我院鲍曼不动杆菌对亚胺培南耐药性变迁及其耐药机制。方法用WHONET-5软件分析1999～2001年我院分离的鲍曼不动杆菌的耐药性变迁;等电聚焦电泳测定酶的等电点;接合试验证实酶基因有无可转移性,并用碱裂解法提取质粒;脉冲场凝胶电泳(pulsedfieldgelelectrophoresis,PFGE)确定耐药株的亲缘关系;对整合酶基因及碳青霉烯酶基因OXA-、IMP-、VIM-进行聚合酶链式反应(polymerasechainreaction,PCR)及序列分析。结果1999～2001年,鲍曼不动杆菌对亚胺培南的耐药性分别为8.5%,1.8%及3.9%。存活的亚胺培南耐药株共9株,这9株菌同时对其他碳青霉烯类、头孢他啶、氨曲南、庆大霉素耐药,其中4株同时对环丙沙星耐药。接合试验证实亚胺培南的耐药基因不能转移,9株菌均不含质粒。9株菌均产多种β内酰胺酶:TEM-1酶,AmpC酶及pI为6.7、6.0的2个酶,后2个酶不被邻氯西林、克拉维酸抑制。所有9株菌均含I类整合酶基因。9株菌IMP-、VIM-型PCR均阴性;但用OXA-23特异引物扩增均阳性,经序列分析证明,100%与OXA-23同源。PFGE发现3个耐药克隆(A型5株,B型3株,C型1株),其中A克隆株与对照克隆株(同时耐头孢他啶、环丙沙星、庆大霉素,但亚胺培南敏感)同源关系密切。
To investigate the mechanism of carbapenems resistance in Acinetobacter baumannii.Methods WHONET-5software was used to analyze the trend of carbapenem resistance in Acinetobacter baumannii collected from1999to2001at Peking Union Medical College Hospital.Analytical isoelectric focusing was used to measure the pI of the beta-lactamase.Conjugation experiment was used to study the transfer of carbapenem resistance and plasmid DNA was extracted and purified with Qiagen Plasmid Mini Kit.The homology of the isolates was determined by pulsed field gel electrophoresis(PFGE).Integrase genes and bla IMP - ,bla VIM- ,bla OXA- genes for resistant isolates were amplified and sequenced.Results Imipenem resistance in A.baumannii was ranged from1.8%～8.5%,but only9resistant isolates were viable.They were co-resistant to other carbapenems,ceftazidime,aztreonam,and gentamicin,and four isolates were resistant to ciprofloxacin.Impipenem resistance could not be transferred to susceptible strains.No plasmid was extracted.Each isolate produced TEM-1,AmpC,and two enzymes(pI 6.7,6.0),which can not be inhibited by cloxacillin and clavulanic acid.Each isolate had class I intergase gene.Nine isolates were all negative for PCR of bla IMP- and bla VIM- genes,but positive for bla OXA -23 specific PCR.Squencing found100%homology with bla OXA -23 .PFGE found3clones(A type:5isolates;B type:3isolates;C type:1isolate).Control isolates(imipenem-susceptible,but ceftazidime,ciprofloxacin,and gentamicin resistant)were also A clone.Conclusions Production of OXA-23carbapenemase in A.baumannii was one of the main mechanisms of carbapenems resistance at our hospital.It brings concern that imipenem-resistant clone has evoluted from nosocomial multiple-resistant strains.
出处
《中国医学科学院学报》
CAS
CSCD
北大核心
2003年第5期567-572,共6页
Acta Academiae Medicinae Sinicae
