Evaluation of Gen-Probe DNA hybridization systems for the identification of Mycobacterium tuberculosis and Mycobacterium avium-intracellulare

The Gen-Probe DNA hybridization system, rapid diagnostic assays for the identification of Mycobacterium tuberculosis (MTB) complex and Mycobacterium avium-intracellulare (MAIC) complex, were evaluated. Designed to identify a primary mycobacterial isolate, the former correctly identified 91 of 92 MTB and all 27 non-MTB isolates and controls when compared with conventional identification methods for a sensitivity of 98.91% and specificity of 100%. The latter correctly identified 63 of 64 MAIC isolates and controls and 31 of 32 non-MAIC isolates and controls when compared with conventional identification methods for a sensitivity of 98.43% and a specificity of 96.87%. The one false positive noted with the MAIC probe was an MTB misidentified as an MAIC. The two false negatives noted above were subsequently shown to be contaminated. The tests are fast and easy to perform and interpret.