Kanamycin Susceptibility Testing of Mycobacterium tuberculosis Using Mycobacterium Growth Indicator Tube and a Colorimetric Method

Two novel systems were evaluated for performing indirect kanamycin susceptibility tests on 72 strains of Mycobacterium tuberculosis. The microplate Alamar blue colorimetric method (breakpoint, 2.5 μg/ml) and the Mycobacterium Growth Indicator Tube (MGIT) system (breakpoint, 5.0 μg/ml) both produced 98.6% agreement when compared with the conventional proportion method performed on 7H10 agar using 5.0 μg of kanamycin/ml. Both systems provided results within an average of 1 week.