title: Ofloxacin resistance in Mycobacterium tuberculosis is associated with efflux pump activity independent of resistance pattern and genotype.
abstract: 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.
authors.affiliation: 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 .
authors.forename: Zhaogang
authors.initials: Z
authors.lastname: Sun
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Xu
authors.forename: Yong
authors.initials: Y
authors.lastname: Sun
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Xuxia
authors.initials: X
authors.lastname: Zhang
authors.forename: Hairong
authors.initials: H
authors.lastname: Huang
authors.forename: Chuanyou
authors.initials: C
authors.lastname: Li
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D005838:Genotype; D008826:Microbial Sensitivity Tests / Q000379:methods; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics*; D015242:Ofloxacin / Q000494:pharmacology*; D018088:Tuberculosis, Multidrug-Resistant / Q000235:genetics*
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D015242:Ofloxacin