产OXA-23鲍曼不动杆菌可移动遗传元件研究

Detection of mobile genetic elements in OXA-23-producing acinetobacter baumannii

目的了解产OXA-23鲍曼不动杆菌(Acinetobacter baumannii,Ab)中整合子、转座子、插入序列及接合性质粒等可移动遗传元件分布状况及其与耐药性的关系。方法收集中南大学湘雅医院2009年1～6月产OXA-23鲍曼不动杆菌71株;根据CLSI2009年标准采用纸片扩散法进行药物敏感性试验;聚合酶链式反应(PCR)检测3种整合子遗传标记(intI 1、intI 2和intI 3)、4种转座子遗传标记(merA、tnpU、tnp513和tnpA)、2种插入序列遗传标记(ISAba1、IS26)及2种接合性质粒遗传标记(traA、trbC),共11种可移动遗传元件;结合药敏结果分析可移动遗传元件与耐药性的关系。结果 intI 1、merA、tnpU、tnp513、ISAba1和IS26检出阳性率分别为:85.9%、7.0%、91.5%、83.1%、100.0%和100.0%。其余5种可移动遗传元件未检出;71株鲍曼不动杆菌每株至少检出2种可移动遗传元件,最多检出6种可移动遗传元件,其中大部分受试菌检出5种可移动遗传元件;在国内首次从鲍曼不动杆菌中检出merA基因,且首次在国内同时从1株鲍曼不动杆菌中检出intI1、merA、tnpU、tnp513、ISAba1和IS26共6种可移动遗传元件;对n<5和n≥5两组耐10种及以上药物菌株比例差异进行χ2检验发现,差异具有显著性(P<0.05),提示可移动遗传元件检出数越高,耐多药菌株数越多,耐药率越高。结论产OXA-23鲍曼不动杆菌易检出各类可移动遗传元件,与医院鲍曼不动杆菌耐药机制相关的可移动遗传元件主要有intI 1、merA、tnpU、tnp513、ISAba1和IS26。

[ Objective ] To investigate the distribution of the mobile genetic elements such as integron, transposon, insertion sequence and conjunction plasmid and the relationship between mobile genetic elements and antibiotic resistance of OXA-23-producing Aeinetobacter baumannii. [Methods ] During January 2009 to June 2009, 71 OXA- 23-producing Acinetobacter baumannii isolates were collected in the clinical microbiology laboratory in Xiangya hospital. Disk diffusion was performed to determine the antimicrobial susceptibility of OXA-23-producing Acineto- bacter baumannii isolates. 11 types of mobile genetic elements such as integron genetic marks （intI 1, intI 2 and intI 3）, transposon genetic marks （merA, tnpU, tnp513 and tnpA）, insertion sequence genetic marks （ISAbal and IS26） and conjunction plasmid genetic marks （traA and trbC） of 71 strains were analyzed by polymerase chain reaction （PCR）, the data combined with antibiotic susceptibilitywere reviewed. [Results] Among 71 strains of OXA-23- producing Acinetobacter baumannii, the positive rates of intI 1, merA, tnpU, tnp513, ISAbal and IS26 were 85.9%, 7.0%, 91.5%, 83.1%, 100.0% and 100.0%, respectively, and the other 5 genes were negative. At least two kinds of mobile genetic elements were found in each strain, at most 6 elements were found in some strains, and most of them were detected carrying 5 kinds of mobile genetic elements. It＇s the first report that merA gene was found positive in Acinetobacter baumannii in China, and the coexistence of six mobile genetic elements intI 1, merA, tnpU, tnpS13, ISAbal and IS26 in Acinetobacter baumannii was also the first report in China. The chi-square test showed that there was a statistically significant difference between two groups （n 〈5 and n ≥5）, which also predicted that the more genetic elements, the more multi-resistant strains, the higher resistant rate. [ Conclusions ] Mobile genetic elements can be mostly found positive in OXA-23-producing Acinetobacter baumannii, and intI1, merA, tnpU, tnp513, ISAbal and IS26 may be the main mobile genetic elements which induce antibiotic resistant mechanism of Acinetobacter baumannii.