In vitro susceptibility testing of levofloxacin and ofloxacin by microtiter plate Alamar blue against multidrug and non multidrug resistant Mycobacterium tuberculosis in Thailand.

Antituberculous drugs for current therapy of multidrugs resistant tuberculosis (MDR-TB) are limited. The in vitro susceptibility of Mycobacterium tuberculosis (MTB) as well as MDR-TB with other antibiotic drugs were determined in order to find alternative drugs for the treatment of MDR-TB. Forty-seven MDR-TB and 62 MTB of clinical isolates were tested against levofloxacin and ofloxacin. The MDR-TB at the MIC90 of levofloxacin and ofloxcain were 1 microg/ml and 2 microg/ml, respectively. Of these MTB, the MIC90 of both drugs were 0.5 microg/ml and 1 microg/ml, respectively. It seemed that levofloxacin MICs of both MDR-TB and MTB were one dilution less than ofloxcin. The promising activity of ofloxacin and levofloxacin against MDR-TB and MTB suggest that both drugs could be used as second-line drugs for MDR-TB or as a good alternative antituberculous drug for patients who have intolerance to the first line drug.