目的阐明体外诱导利奈唑胺耐药粪肠球菌的核糖体23SrRNA V区基因位点变异特征。方法收集1株血流感染的粪肠球菌和1株粪肠球菌质控菌ATCC29212(编号分别为F3和F4菌株,均为利奈唑胺敏感株),通过体外浓度倍增法诱导利奈唑胺耐药;挑取单克隆,经E-test条测定MIC值,获得各菌株的耐药浓度梯度;提取耐药菌株基因组DNA,PCR扩增23SrRNA V区基因,扩增产物经测序后与野生株比较,获得V区的突变位点。结果经体外多步法诱导利奈唑胺耐药的不同MIC值粪肠球菌共13株。PCR测序分析2株母株均无变异位点,23SrRNA V区的突变位点主要是G2576U,此外还有T2504A、G2505A、C2610A、C2424U。结论体外多步法可诱导粪肠球菌利奈唑胺耐药,耐药机制与23SrRNA V区位点突变密切相关,突变位点随着MIC值的增高而增多。
Objective To investigate the characteristics of genetic mutations in the V domain of the 23Sribosomal RNA gene of linezolid-resistant Enterococcus faecalis in vitro. Methods A strain of E.faecalis isolated from clinical samples(designated F3)and a strain of E.faecalis(designated F4)that is commonly used as a quality control strain in antibiotic tests(ATCC 29212)were obtained.Linezolid(LZD)resistance was induced in vitro via serial dilution.The 2parent strains,F3and F4,and LZD-resistant strains were isolated and their MIC values were determined using an E-test. The V domain of the 23Sribosomal RNA gene of these strains was then amplified and sequenced. Results LZD resistance was induced in vitroin 13strains of E.faecalis with different MIC values.PCR and sequencing indicated that the V domain of the 23Sribosomal RNA gene of these strains contained multiple point mutations,including G2576U,T2504A, G2505A,C2610A,and C2424U. Conclusion LZD resistance can be induced in E.faecalis in vitro.LZD resistance in E.faecalis was closely associated with genetic mutations in the V domain of the 23Sribosomal RNA gene,and the MIC value increased with a larger number of point mutations in the ribosomal RNA gene.