Abstract: Objective To explore the MICs’ distribution of ofloxacin,levofloxacin and ciprofloxacin against clinical isolate of Mycobacterium tuberculosis in vitro strains.Methods The MICs of these drugs were determined by equivalent dilution method.Results Of 21 clinical isolates of M.tuberculosis not previously exposed,and of 15 clinical isolates previously exposed within 4 weeks to these drugs,the MICs of 20 (95.2%) and 13(86.7%) respectively were closed to that of Mycobacterium tuberculosis H₃₇Rv’s,of 16 isolates of M.tuberculosis previously exposed beyond 4 weeks,MICs of 15 isolates (93.7%) were higher than that of H₃₇Rv.Conclusion If the three drugs were treated patients with tuberculosis for a long time,the MICs of M.Tuberculosis of these drugs might be increased.

Key words: Mycobacterium,tuberculosis, Fluoroquinlones/pharmacokin