In vitro activity of linezolid and moxifloxacin against multidrug-resistant Mycobacterium tuberculosis using a rapid method

NORA MORCILLO; BELÉN IMPERIALE; MÓNICA PONTINO; BEATRÍZ DI GIULIO

Paris

Congreso; IUTLD Congreso. Paris, Francia 3 al 6 de noviembre 2006; 2006

IUTLD

Tuberculosis caused by multidrug-resistant Mycobacterium tuberculosis strains (MDR-TB) is considered an emergent health problem frequently associated to HIV positive patients. Currently used antituberculosis treatments often fail and others drugs different from those included in the standard chemotherapy must be used. Minimal inhibitory concentration (MIC) of linezolid (LZ) and moxifloxacin (MOX) were determined by a colorimetric microplate-based method using 3-(4,4-Dimethylthiazollyl-2)-2,5 Diphenyl Tetrazolium Bromide (M-MTT). MIC50 and MIC90 for each drug were also determined. The tested drugs range concentrations (mg/L) were: LZ, 2.00 to 0.06 and MOX 1.00 to 0.03. The assay was carried out on 35 MDR-TB isolated in Argentina during 2005. MIC50 and MIC90 for LZ were 0.25 and 0.50 mg/L respectively, while for MOX these figures were 0.06 and 0.25 mg/L. Results of MICs by M-MTT were obtained in an average of 8 days and they were compared to those obtained by the agar proportion method (PM) containing 2.0 mg/L of LZ and 1.0 mg/L of MOX. Full agreement between results obtained by both methods was observed. The microplate system could be used as a simple, rapid and low cost technology to explore susceptibility of MDR-TB strains to several potential antituberculosis drugs as MOX and LZ.