Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Hokkaido, Japan.
PLoS Negl Trop Dis. 2012;6(10):e1838. doi: 10.1371/journal.pntd.0001838. Epub 2012 Oct 11.
Ofloxacin is a fluoroquinolone (FQ) used for the treatment of leprosy. FQs are known to interact with both A and B subunits of DNA gyrase and inhibit supercoiling activity of this enzyme. Mutations conferring FQ resistance have been reported to be found only in the gene encoding A subunit of this enzyme (gyrA) of M. leprae, although there are many reports on the FQ resistance-associated mutation in gyrB in other bacteria, including M. tuberculosis, a bacterial species in the same genus as M. leprae.
METHODOLOGY/PRINCIPAL FINDINGS: To reveal the possible contribution of mutations in gyrB to FQ resistance in M. leprae, we examined the inhibitory activity of FQs against recombinant DNA gyrases with amino acid substitutions at position 464, 502 and 504, equivalent to position 461, 499 and 501 in M. tuberculosis, which are reported to contribute to reduced sensitivity to FQ. The FQ-inhibited supercoiling assay and FQ-induced cleavage assay demonstrated the important roles of these amino acid substitutions in reduced sensitivity to FQ with marked influence by amino acid substitution, especially at position 502. Additionally, effectiveness of sitafloxacin, a FQ, to mutant DNA gyrases was revealed by low inhibitory concentration of this FQ.
Data obtained in this study suggested the possible emergence of FQ-resistant M. leprae with mutations in gyrB and the necessity of analyzing both gyrA and gyrB for an FQ susceptibility test. In addition, potential use of sitafloxacin for the treatment of problematic cases of leprosy by FQ resistant M. leprae was suggested.
氧氟沙星是一种氟喹诺酮（FQ）药物，用于治疗麻风病。已知 FQ 会与 DNA 回旋酶的 A 和 B 亚基相互作用，并抑制该酶的超螺旋活性。虽然有许多关于其他细菌（包括与麻风分枝杆菌同属的结核分枝杆菌）gyrB 中与 FQ 耐药相关的突变的报道，但仅在麻风分枝杆菌该酶的 A 亚基（gyrA）基因中发现了赋予 FQ 耐药性的突变。
方法/主要发现：为了揭示 gyrB 突变对麻风分枝杆菌 FQ 耐药性的可能贡献，我们检查了氨基酸取代位置 464、502 和 504 的重组 DNA 回旋酶对 FQ 的抑制活性，这些位置相当于结核分枝杆菌的位置 461、499 和 501，据报道这些位置的突变有助于降低对 FQ 的敏感性。FQ 抑制超螺旋实验和 FQ 诱导切割实验表明，这些氨基酸取代在降低对 FQ 的敏感性方面发挥了重要作用，尤其是在位置 502。此外，通过该 FQ 的低抑制浓度揭示了 FQ 对突变型 DNA 回旋酶的有效性。
本研究获得的数据表明，gyrB 突变可能导致 FQ 耐药性麻风分枝杆菌的出现，有必要对 gyrA 和 gyrB 进行分析以进行 FQ 药敏试验。此外，还提示了使用司氟沙星治疗由 FQ 耐药麻风分枝杆菌引起的麻风病的潜在应用。
