摘要
目的了解鲍曼不动杆菌对亚胺培南产生耐药的分子机制.方法收集对亚胺培南耐药的鲍曼不动杆菌(imipenem resistant Acinetobacter baumannii,IRAB)无重复株共9株,采用琼脂稀释法进行药敏检测,协同抑制试验、质粒接合试验、Southern杂交、等电聚焦电泳、PCR扩增blaVIM、blaIMP、blaOXA-23、blaOXA-24相关基因及整合子编码序列及其分子克隆和测序,以阐述其分子耐药机制.结果本组IRAB具有多重耐药性;耐药基因分子克隆、测序并结合等电聚焦分析证实均产OXA-23型碳青霉烯酶,质粒接合试验、Southern杂交显示其编码基因定位在染色体上.9株细菌均检测出Ⅰ型整合子基因结构(大小约1.2～4kb);3株菌检测出Ⅱ型整合子基因结构(1.8～2kb),均携带了多种耐药基因.结论产OXA-23型β-内酰胺酶是本组鲍曼不动杆菌对碳青霉烯类抗生素产生耐药性的重要原因;IRAB整合子基因携带的多种耐药基因与其多重耐药性相关.
Objective To investigate the molecular mechanism of carbapenem resistance in imipenem resistant A.baumannii (IRAB). Methods Nine clinical isolates of non-repetitive IRAB were collected. Initially, all the strains were studied by antimicrobial susceptibility test and analytical isoelectric focusing (IEF); Then the chromosome DNA of the isolates were undergone PCR with the primers of bla _ VIM , bla _ IMP , bla _ OXA-23-like , bla _ OXA-24-like genes ; the primers of I, -II, -III type integrases and the primers of the corresponding integrons 5′- and 3′- conserved sections. Plasmid conjugation experiments were done to study the transfer of carbapenem resistance. The gene location of bla _ OXA-23 was studied by DNA membrane hybridization with bla _ OXA-23 probe to the chromosomal DNA and the integron-conserved sections. Results All the isolates were highly resistant to imipenem, meropenem and almost all the antibiotics tested; the results of molecular cloning, DNA sequencing and isoelectric focusing showed that all the isolated have OXA-23 type carbapenemases; plasmid conjugation experiments, DNA hybridization, together with DNA sequencing, suggest that bla _ OXA-23 is chromosomally located. All the isolates have class I integron structure gene (about 1.2～4kb) and 3 have class II integron(1.8～2kb), harboring vary kinds of resistant genes except bla _ OXA-23 . Conclusions OXA-23 production is an important factor to carbapemen reistance and these resistant genes in integrons are responsible for multi-resistance of the A.baumannii isolates studied.
出处
《中国抗生素杂志》
CAS
CSCD
北大核心
2005年第4期217-221,240,共6页
Chinese Journal of Antibiotics
