质粒介导的鲍曼不动杆菌 blaoxa-23耐药基因研究

摘要

目的：了解质粒介导的碳青霉烯类耐药基因blaoxa-23在鲍曼不动杆菌中的表达，分析其与耐药性的关系，探讨blaoxa-23水平传播方式。方法收集临床分离的鲍曼不动杆菌共101株，采用琼脂稀释法检测菌株对碳青霉烯类抗菌药物的耐药性；多位点序列分型法分析耐碳青霉烯类鲍曼不动杆菌（ Carbapenem-resistant Acinetobacter baumannii， CRAB ）的同源性；PCR 扩增β-内酰胺酶基因（blaoxa-23、blaoxa-24、blaoxa-51、blaoxa-58、blaIMP-1、blaVIM-1／2和 blaAmp-C ）并检测 blaoxa-23所在的转座子结构；Southern杂交确定blaoxa-23定位的质粒，接合转化试验探讨携带blaoxa-23质粒的水平传播。结果101株鲍曼不动杆菌对碳青霉烯类药物的耐药率较高，对亚胺培南和美罗培南的耐药率分别为64.4％和69.3％。共检测出56株CRAB，多位点序列分型（ multilocus sequence typing ，MLST）显示ST208型占50％（28／56），是CRAB 的主要克隆型。所有 CRAB 菌株均携带 blaoxa-23和 blaoxa-51，携带 blaIMP-1和blaAmp-C的菌株分别为78.6％（44／56）和96.4％（54／56）；未检测到blaoxa-24、blaoxa-58或blaVIM-1／2基因。56株CRAB 中，54株blaoxa-23位于Tn2008转座子，其余2株位于Tn2006转座子，未检测到Tn2007转座子。质粒电泳显示菌株携带2～4个质粒， Southern 杂交证实 blaoxa-23位于质粒上。接合试验证实blaoxa-23可通过质粒传播。结论临床分离鲍曼不动杆菌对碳青霉烯类耐药率较高，临床存在CRAB播散流行，ST208型是主要克隆株；blaoxa-23表达在鲍曼不动杆菌碳青霉烯类耐药中发挥重要作用；该基因可通过Tn2008转座子上载高活动能力的质粒，导致CRAB传播。（中华检验医学杂志，2017，40：36-40）%Objective To investigate the prevalence and transmission mechanisms of plasmid-mediated blaoxa-23 resistance genes in Acinetobacter baumannii.Methods One hundred and one Acinetobacter baumannii were collected from Obstetrics and Gynecology Hospital of Fudan University and Renji Hospital Shanghai Jiaotong University School of Medicine.Antibiotic susceptibility of carbapenems were determined by standard agar dilution method.Molecular typing of Carbapenem-resistant Acinetobacter baumannii (CRAB) was performed by MLST.blaoxa-23、blaoxa-24、blaoxa-51、blaoxa-58、blaIMP-1、blaVIM-1/2 and blaAmp-C were analyzed by PCR.The analysis of blaoxa-23 transposons for carbapenems resistant A.baumannii isolates was also performed by PCR.Plasmid was analyzed by gel electrophoresis.Conjugation experiments were performed to determine the transferability of blaoxa-23.Results The antibiotic susceptibility tests showed the resistant rates to carbapenems were extremely high , and the ones of imipenem and meropenem were 64.4%and 69.3%.Fifty-six (53%) isolates were carbapenems-resistant A.baumannii.Main clone ST208 includes 28 isolates(50%) in CRAB.A total of the CRAB isolates harbored blaoxa-23 and blaoxa-51 (100%), 44 for blaIMP-1(78.6%) and 54 for blaAmp-C(96.4%), while blaoxa-24, blaoxa-58 and blaVIM-1/2 was undetected.Two previously identified transposons ( Tn2006 and Tn2008 ) was found in the isolates.Plasmid gel electrophoresis results showed that the isolates carried 2-4 plasmids and blaoxa-23 were transferable by plasmids.Conclusions There is high carbapenems resistance of A.baumannii infections.ST208 was the most prevalent molecular type.The mainly drug-resistant genes of A.baumannii are blaoxa-23.Based on the findings, blaoxa-23 is plasmid mediated, suggesting that it may transfer by plasmids carrying Tn 2008 transposon, thus induced isolates resistant to carbapenemase.