16S rRNA甲基化酶在氨基糖苷类抗生素耐药革兰阴性菌中的分布

Widespread of 16S rRNA methylases in different species of aminoglycoside-resistant Gram-negative bacilli

目的了解6种编码16SrRNA甲基化酶的基因在氨基糖苷类抗生素耐药革兰阴性菌中的流行情况。方法收集本院2007年10—12月分离的211株阿米卡星和庆大霉素耐药革兰阴性菌,采用PCR检测其中6种甲基化酶基因(armA、rmtA、rmtB、rmtC、rmtD和npmA)的分布。对16SrRNA甲基化酶基因阳性的菌株,用ERIC-PCR进行同源性分析。结果 211株阿米卡星和庆大霉素耐药革兰阴性菌中,91.5%(193/211)被检出16SrRNA甲基化酶基因,其中133株含armA(133/211,63.0%),60株含rmtB(60/211,28.4%)。阿米卡星MIC≥512mg/L、庆大霉素MIC≥128mg/L的104株肠杆菌科细菌中,甲基化酶基因检出达100%,且armA和rmtB的检出相仿(分别为49与55株)。阿米卡星MIC≥512mg/L、庆大霉素MIC≥128mg/L的94株铜绿假单胞菌和鲍曼不动杆菌中,甲基化酶检出94.7%(89株),以armA(84株)为主。未检测到rmtA,rmtC,rmtD和npmA基因。ERIC-PCR结果显示该类基因并非单克隆传播。结论几乎所有临床分离的阿米卡星MIC>512mg/L的革兰阴性菌中都能检出armA或rmtB基因。

Objective To investigate the distribution of methylase genes in more than 200 aminoglycoside resistant Gram-negative clinical isolates collected in 2007. Methods The 16S rRNA methylase genes were amplified by PCR in 211 consecutive clinical isolates of Gram-negative bacilli resistant to gentamicin and amikacin by agar dilution. Results The 16S rRNA methylase genes were present in 91.5% （193/211） of clinical isolates resistant to amikacin and gentamicin, of which arrnA and rmtB were identified in 63.0% and 28.4% of the strains, respectively, arrnA or rrntB gene was identified in all the 104 strains of Enterobacteriacae with amikacin MICs≥512 mg/L and gentamicin MICs≥128 mg/L. These two genes were almost equally represen ted （49 vs. 55 strains）. Genes for arrnA or rrntB were detected in 94.7% （89/94） of Acinetobacter baurnannii and Pseudornonas aeruginosa strains with amikacin MICs≥512 mg/L and gentamicin MICs≥128 mg/L, and armA was predominant （84 vs. 5 strains with rmtB）. No rmtA, rmtC, rrntD or npmA gene was found. ERIC-PCR indicated that arrnA and rrntB genes were spread by both horizontal transfer and clonal dissemination. Conclusions 16S rRNA methylase genes, arrnA or rmtB, were present in almost all clinical isolates with amikacin MICs 〉 512 mg/L.