Objective To explore the presence of 16S rRNA methylase genes in Acinetobacter baumannii which is double-circle resistant to aminoglycoside antibiotic in K-B methods, and to analyze the expression levels of resistance genes mRNA among strains induced and non-induced by amikacin. Methods A total of 42 strains of Acinetobacter baumannii were collected to test the antibiotic susceptibility by disk diffusion method. The three kinds of 16S rRNA methylase genes-armA, rmtB and rmtC were amplified by PCR. The genes expressions in drug-induced strains and non-induced strains were respectively measured by PT-PCR. Results About 90.4%(38/42) of strains showed the phenomenon of double-circle resistance. The armA was detected in these strains, but the rmtB and rmtC were not found. In other strains, 3 strains showed susceptible and 1 strain showed common resistant, and thel6S rRNA methylase genes were not found in these four strains. The result of PT-PCR revealed that the expression level of armA gene mRNA was significantly up-regulated when the strains were induced by amikacin. Conclusion The phenomenon of double-circle is possibly associated with the inducible expression ofarmA.%目的 探讨在K-B法药物敏感试验中对氨基糖苷类药物双圈耐药的鲍曼不动杆菌16S rRNA甲基化酶基因携带状况以及药物诱导对该基因mRNA表达量的影响.方法 收集42株鲍曼不动杆菌,K-B法测定其药敏情况；PCR法扩增三种16S rRNA甲基化酶基因armA、rmtB及rmtC;用RT-PCR的方法分析阿米卡星诱导前后耐药基因表达量.结果 90.4％(38/42)的菌株阿米卡星药敏纸片周围呈现双圈耐药,且均检测到armA,未检测到rmtB及rmtC,其余3株为敏感,1株为普通耐药,且PCR检测耐药基因为阴性.RT-PCR结果显示经阿米卡星诱导后细菌armA基因mRNA表达量显著上升.结论 双圈耐药现象与armA基因诱导型表达有关.
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