Comparison between radiometric and proportional methodologies in susceptibility testing of mycobacteria other than tubercle bacilli (MOT)

109 strains of mycobacteria other than tubercle bacilli (MOT) were tested against four primary antituberculous drugs; 27 strains of M. tuberculosis served as controls. While the latter species showed excellent overall agreement with the reference (proportion) method of Canetti (particularly for sensitive strains), MOTT gave such results only if there was a prevalence of sensitive or resistant strains in a species. Since this could not be predicted, the radiometric method cannot substitute for the proportion method for susceptibility testing of MOTT, in spite of early availability of results.