Accumulation of five fluoroquinolones by Mycobacterium tuberculosis H37R

The accumulation of ciprofloxacin, norfloxacin, moxifloxacin, levofloxacin and ofloxacin by Mycobacterium tuberculosis H37Rv was determined with a modified fluorescence method. The time to achieve a steady-state concentration (SSC) of each agent in M. tuberculosis was 60-240 s. Moxifloxacin was accumulated to the lowest concentration and ciprofloxacin to the highest. However, ciprofloxacin took longer to achieve an SSC than the other four agents; levofloxacin reached steady state in the shortest time. Larger fluoroquinolones accumulated to the lowest concentration and more slowly. Although all five agents had low hydrophobicity values (P(app) <or =0.11), those with the lowest values accumulated to the higher concentrations.