Sun Zhaogang, Xu Yuhui, Sun Yong, Liu Yi, Zhang Xuxia, Huang Hairong, Li Chuanyou
Beijing Key Laboratory in Drug Resistant Tuberculosis Research, Beijing Tuberculosis and Thoracic Tumor Research Institute, Beijing Chest Hospital, Capital Medical University , Beijing, People's Republic of China .
Microb Drug Resist. 2014 Dec;20(6):525-32. doi: 10.1089/mdr.2013.0171.
Drug-resistance to ofloxacin (OFX) in Mycobacterium tuberculosis is due to missense mutations in gyrA and other factors, such as alterations in the activity of drug efflux pumps. In this study, we identified 8 extensively drug resistant tuberculosis (XDR-TB), 40 multidrug resistant TB (MDR-TB), 38 polydrug resistant TB (PDR-TB), and 16 single OFX-resistant TB from 102 clinical isolates. We tested the effect of three efflux inhibitors, reserpine, verapamil, and carbonyl cyanide m-chlorophenyl hydrazone (CCCP), on changes in the OFX minimum inhibitory concentration (MIC) using Resazurin microtitre assay. These three inhibitors changed the MICs from 2- to 32-fold, with CCCP having the strongest effect. A total of 55%, 74%, and 83% of the tested isolates had changes in MIC of more than two-fold by reserpine, verapamil, and CCCP, respectively. The inhibitors led to similar fold-changes of OFX MICs in the XDR, MDR, PDR, and single OFX-resistant isolates. For each inhibitor, a higher resistance to OFX was associated with the greater efflux pump activity. There were no significant differences in the effect of efflux pump inhibitors upon Beijing and non-Beijing M. tuberculosis genotypes. Taken together, these results indicate that the efflux pump activity was greater in the isolates higher resistant to OFX and had similar effects on isolates with different drug resistant pattern, and had similar effects on Beijing and non-Beijing genotypes.
结核分枝杆菌对氧氟沙星（OFX）的耐药性是由于gyrA基因的错义突变以及其他因素，如药物外排泵活性的改变。在本研究中，我们从102株临床分离株中鉴定出8株广泛耐药结核病（XDR-TB）、40株多药耐药结核病（MDR-TB）、38株耐多药结核病（PDR-TB）和16株单耐氧氟沙星结核病。我们使用刃天青微量滴定法测试了三种外排抑制剂利血平、维拉帕米和羰基氰化物间氯苯腙（CCCP）对氧氟沙星最低抑菌浓度（MIC）变化的影响。这三种抑制剂使MIC变化了2至32倍，其中CCCP的作用最强。分别有55%、74%和83%的测试分离株经利血平、维拉帕米和CCCP处理后MIC变化超过两倍。这些抑制剂在XDR、MDR、PDR和单耐氧氟沙星分离株中导致氧氟沙星MIC有相似倍数的变化。对于每种抑制剂，对氧氟沙星的耐药性越高，外排泵活性越高。外排泵抑制剂对北京和非北京基因型的结核分枝杆菌的作用没有显著差异。综上所述，这些结果表明，对氧氟沙星耐药性较高的分离株中外排泵活性更高，对不同耐药模式的分离株有相似作用，对北京和非北京基因型也有相似作用。
