Williams K J, Chung G A, Piddock L J
Department of Infection, The Medical School, University of Birmingham, Edgbaston, United Kingdom.
Antimicrob Agents Chemother. 1998 Apr;42(4):795-800. doi: 10.1128/AAC.42.4.795.
The modified fluorescence method was used to determine the accumulation of norfloxacin by Mycobacterium aurum A+ and Mycobacterium smegmatis mc(2)155. By using an exogenous norfloxacin concentration of 10 microg/ml, a steady-state concentration (SSC) of 160 to 180 ng of norfloxacin/mg of cells was obtained for M. aurum, and an SSC of 120 to 140 ng of norfloxacin/mg of cells obtained for M. smegmatis. For both species of mycobacteria, the SSC was achieved within 5 min. The silicon oil method was investigated and gave higher SSCs than the modified fluorescence method. Further studies on the mechanism of norfloxacin accumulation by M. aurum were performed. An increase in the pH of the wash buffer from 7.0 to 9.0 did not significantly affect the final SSC obtained. Accumulation was nonsaturated over a norfloxacin concentration range of 0 to 100 microg/ml, and the proton motive force inhibitor 2,4-dinitrophenol (1 and 2 mM), whether it was added before or after norfloxacin was added, had no effect on the final SSC obtained. 2,4-Dinitrophenol also had no effect on norfloxacin accumulation by M. smegmatis. Furthermore, norfloxacin accumulation by M. aurum was unaffected by the presence of either Tween 80 or subinhibitory concentrations of ethambutol in the growth medium. Therefore, it is proposed that norfloxacin accumulation by mycobacteria occurs by simple, energy-independent diffusion.
采用改良荧光法测定了金色分枝杆菌A+和耻垢分枝杆菌mc(2)155对诺氟沙星的积累情况。在外源诺氟沙星浓度为10微克/毫升的情况下，金色分枝杆菌的诺氟沙星稳态浓度（SSC）为160至180纳克/毫克细胞，耻垢分枝杆菌的SSC为120至140纳克/毫克细胞。对于这两种分枝杆菌，5分钟内即可达到SSC。对硅油法进行了研究，其得到的SSC高于改良荧光法。对金色分枝杆菌积累诺氟沙星的机制进行了进一步研究。洗涤缓冲液的pH从7.0增加到9.0对最终获得的SSC没有显著影响。在0至100微克/毫升的诺氟沙星浓度范围内，积累是非饱和的，质子动力抑制剂2,4-二硝基苯酚（1和2毫摩尔），无论在添加诺氟沙星之前还是之后添加，对最终获得的SSC都没有影响。2,4-二硝基苯酚对耻垢分枝杆菌积累诺氟沙星也没有影响。此外，生长培养基中吐温80或亚抑制浓度的乙胺丁醇的存在对金色分枝杆菌积累诺氟沙星没有影响。因此，提出分枝杆菌积累诺氟沙星是通过简单且不依赖能量的扩散发生的。
