Activity of Moxifloxacin Against Ofloxacin-Resistant Mycobacterium Tuberculosis: A Study of Cross-Resistance Between Ofloxacin and Moxifloxacin / 결핵및호흡기질환

ABSTRACT

BACKGROUND: Moxifloxacin is an 8-methoxyquinolone compound which has been shown to have the best activity of the quinolones against M. tuberculosis but there is no literature showing the rate of cross-resistance between moxifloxacin and the other quinolones such as ofloxacin. Therefore, we tested the activity of moxifloxacin against ofloxacin resistant M. tuberculosis by a study of cross-resistance. METHODS: We tested MIC's of moxifloxacin and ofloxacin by proportion method against 34 M. tuberculosis isolates showing resistance against ofloxacin at 2.5microgram/ml concentration and 13 ofloxacin susceptible isolates from specimens submitted to clinical laboratory of National Masan Hospital from March 2003 to March 2004. RESULTS: For ofloxacin susceptible isolates, MIC(50) and MIC(90) of ofloxacin were all 1.25 microgram/ml, and MIC(50) and MIC(90) of moxifloxacin were 0.31 microgram/ml and 0.63microgram/ml respectively. For ofloxacin resistant isolates, MIC(50) of ofloxacin was over 10microgram/ml and MIC(50) of moxifloxacin was 5microgram/ml,MIC(90) of ofloxacin and moxifloxacin were all over 10microgram/ml. The rate of cross-resistance between the two was 67.6%(23/34) at 2.5microgram/ml concentration. CONCLUSIONS: Moxifloxacin showed activity against 82.4%(28/34) of ofloxacin resistant M. tuberculosis at 10microgram/ml, but more studies are needed so that moxifloxacin will be used for patient with multi-drug resistant tuberculosis including ofloxacin resistance.