To evaluate the association between mutations in the genes gyrA/B and resistance levels to fluoroquinolones in clinical isolates of Mycobacterium tuberculosis, a total of 80 ofloxacin-resistant isolates collected in 2009 by the Shanghai Municipal Centers for Disease Control and Prevention were studied. The minimum inhibitory concentration (MIC) of ofloxacin, moxifloxacin and gatifloxacin for each isolate was determined using the microscopic observation drug susceptibility assay. Sequencing was used to identify mutations in the quinolone resistance-determining region (QRDR) of the gyrA and gyrB genes. In total, 68 isolates had mutations in gyrA, three isolates had mutations in gyrB, six isolates had mutations in both gyrA and gyrB, and three isolates had no mutations. Two common mutations in gyrA, the D94G and D94N mutations, were associated with higher-level resistance to all three fluoroquinolones than two other common mutations (A90V and D94A). Understanding the relationship between MICs and mutations in ofloxacin-resistant isolates will facilitate the optimization of the use of new-generation fluoroquinolones to treat patients with ofloxacin-resistant tuberculosis (TB).

目的 研究异质性耐药对MTB基因型耐药检测结果的影响.方法 选择上海市疾病预防控制中心在2009年收集的80株氧氟沙星临床耐药菌株,利用基因测序检测菌株在gyrA和gyrB耐药决定区的基因突变情况,再用分子克隆和荧光定量PCR探针熔解曲线法,分析经基因测序未检测到耐药突变的菌株中是否存在异质性耐药现象.结果 基因测序报告显示,80株氧氟沙星耐药菌株中有15株未发现已知gyrA或gyrB耐药决定区的基因突变.测序图谱及分子克隆和探针熔解曲线法分析结果表明,其中14株菌株含有已知gyrA耐药突变,即存在异质性耐药现象.纳入异质性耐药的菌株后,基因型与表型耐药检测的符合率从81.3％(65/80)提高到98.8％(79/80).结论 异质性耐药是导致表型和基因型耐药检测结果不符的重要原因.为排除异质性耐药对耐药基因检测的影响,提高基因型与表型耐药检测结果的一致性,需要开发应用更敏感的基因型耐药检测技术,以提高耐药结核病快速检测水平.