中文摘要：

目的调查国内6个省市25家医院临床分离鲍曼不动杆菌中介导高水平氨基糖苷类抗生素耐药的16SrRNA甲基化酶基因armA、rmtA、rmtB的分布情况。方法收集2004年12月-2005年12月国内6省市8家省级医院、浙江省11个地区17家市级医院临床分离的700株鲍曼不动杆菌。琼脂稀释法测定其对妥布霉素、阿米卡星、庆大霉素、异帕米星、奈替米星5种氨基糖苷类抗生素的最低抑菌浓度（MIC）值；PCR筛选三种甲基化酶基因armA、rmtA、rmtB，克隆测序明确基因型；脉冲场凝胶电泳（PFGE）分析菌株的同源性；质粒抽提、接合试验及Southern杂交确定armA基因定位。结果对妥布霉素、阿米卡星、庆大霉素、异帕米星、奈替米星的耐药率分别为67．7％、70．9％、75．7％、63．5％和71．5％。对5种氨基糖苷类抗生素全部耐药的菌株有377株，其中334株检出armA基因；未发现rmtA、rmtB阳性菌株。armA基因阳性菌株PFGE分型以A、B、C为主。碱裂解法反复抽提未得到质粒，多次接合试验未成功；Southern杂交显示，armA基因分别位于克隆A、B、c菌株染色体ApaⅠ酶切PFGE约220、300、220kb大小的PFGE片段上。结论16SrRNA甲基化酶基因armA在鲍曼不动杆菌中广泛存在，armA基因位于鲍曼不动杆菌的染色体上。

英文摘要：

Objective To investigate the prevalence of 16S rRNA methylases genes, armA, rmtA and rmtB, which mediate high level aminoglycoside antibiotics resistance, in Acinetobacter baurnannii isolates from 25 hospitals of 6 cities in China. Methods A total of 700 Acinetobacterbaurnannil isolates were collected from 8 provincial hospitals in 6 cities and 17 local hospitals in 11 regions of Zhejiang Province from Dec. 2004 to Dec. 2005. The minimal inhibitory concentrations （MIC） of these strains to tobramycin, amikacin, gentamycin, isepamicin and netilmicin were determinated using agar dilution. Three 16S rRNA methylase genes, armA, rmtA and rmtB, were detected by PCR- based assays. PCR products were purified, cloned and sequenced. The homology of armA-positive strains was analyzed by pulse-field gel electrophoresis（PFGE）, armA gene mapping was performed by plasmid extraction, conjugation and Southern blot. Results The resistance rates to tobramycin, amikacin, gentamycin, isepamicin, netilmicin were 67. 7%, 70. 9%, 75. 7%, 63. 5%, and 71. 5%, respectively. Three hundred and seventy seven stains were resistant to all these five antibiotics, among which 334 isolates were armA-positive and neither rmtA nor, rmtB gene was detected. Three hundred and thirty four armA-positive isolates were mainly classified into 3 clones by PFGE analysis.No plasmid was extracted and conjugation was not successful, despite multiple attempts of alkaline lysis. Southern blot showed that armA gene was respectively located on 220, 300 and 220 kb on Apa Ⅰ digested DNA fragments of clone A, B and C chromosome of these strains. Conclusions 16S rRNA methylases gene, armA is prevalent in Acinetobacter baumannii and located on Acinetobacter baumannii chromosome.