Susceptibility of Mycobacterium tuberculosis strains to gatifloxacin and moxifloxacin by different methods

Chemotherapy. 2006;52(4):190-5. doi: 10.1159/000093486. Epub 2006 May 22.


Background: Considering the potentials of gatifloxacin and moxifloxacin in the treatment of tuberculosis, the present study was aimed to define resistance to both these drugs.

Methods: Fifty Mycobacterium tuberculosis isolates, consisting of 30 ofloxacin-susceptible and 20 ofloxacin-resistant strains, were tested for their susceptibility to gatifloxacin and moxifloxacin using different susceptibility testing methods, namely the absolute concentration method on Lowenstein-Jensen medium (LJ), the proportion susceptibility testing method (PST) on LJ and 7H11 agar media, and the BACTEC radiometric method.

Result: The minimal inhibitory concentration (MIC) of gatifloxacin and moxifloxacin was 1 microg/ml by the absolute concentration method on LJ. In the PST method on LJ and 7H11, using a criterion of > or =1% growth as resistant, there was 100% agreement with the absolute concentration method at a concentration of 0.5 microg/ml for gatifloxacin, and 96% agreement with the BACTEC method at a concentration of 0.25 microg/ml. For moxifloxacin, results by the PST method showed 96% agreement with the absolute concentration method on LJ at a concentration of 1 microg/ml and 92% agreement at a concentration of 0.5 microg/ml for both the absolute concentration method on 7H11 and the BACTEC method.

Conclusions: The MICs of gatifloxacin and moxifloxacin were much lower than the MICs of other quinolones like ofloxacin and ciprofloxacin. Additionally, these two drugs have shown a low mean MIC and low concentration as a definition of resistance, which might help in treating the patients with low levels of quinolone resistance.

Publication types

  • Comparative Study

MeSH terms

  • Anti-Infective Agents / pharmacology*
  • Aza Compounds / pharmacology*
  • Drug Resistance, Bacterial*
  • Fluoroquinolones / pharmacology*
  • Gatifloxacin
  • Humans
  • Microbial Sensitivity Tests
  • Moxifloxacin
  • Mycobacterium tuberculosis / drug effects*
  • Quinolines / pharmacology*


  • Anti-Infective Agents
  • Aza Compounds
  • Fluoroquinolones
  • Quinolines
  • Gatifloxacin
  • Moxifloxacin