Evaluation of rapid radiometric method for drug susceptibility testing of Mycobacterium tuberculosis

Abstract

A total of 106 isolates of M. tuberculosis were tested for drug susceptibility by the conventional 7H11 plate method and by a new rapid radiometric method using special 7H12 liquid medium with 14C-labeled substrate. Results obtained by the 2 methods were compared for rapidity, sensitivity and specificity of the new test method. There was 98% overall agreement between the results obtained by the 2 methods. Of a total of 424 drug tests, only 8 drug results did not agree, mostly in the case of streptomycin. This new procedure was rapid, with 87% of the test results reportable within 4 days and 98% reportable within 5 days as compared to the usual 3 wk required with the conventional indirect susceptibility test method. The rapid radiometric method seems to have the potential for routine laboratory use and merits further investigations.