Standartization of broth microdilution method for Mycobacterium tuberculosis

Indirect drug susceptibility tests of Mycobacterium tuberculosis was done t o investigate the accuracy and feasibility of a broth microdilution method (BMM) for determining minimal inhibitory concentrations of conventional dru gs against M. tuberculosis. Test drugs included isoniazid (H), rifampicin ( R), ethambutol (E), streptomycin (S) and pyrazinamide (Z). Fifty isolates o f M, tuberculosis from patients who had never received drug therapy, and H3 7Rv Strain for control, were evaluated in the system. When comparing this m ethod with the gold standard proportional method in Lowenstein-Jensen mediu m, sensitivity of 100% for all drugs and specifities of 91, 100, 96, 98 and 85% were observed respectively for H, R, E, S and Z. The BMM was read fast er (14-20 days) than the proportional method (20-28 days). The microdilutio n method evaluated alloys the testing of multiple drugs in multiple concent rations. It is easy to perform and does not require special equipment ol ex pensive supplies. In contrast to radiometric method it does not use radioac tive material.