Comparison of the mycobacteria growth indicator tube with MB redox, Lowenstein-Jensen, and Middlebrook 7H11 media for recovery of mycobacteria in clinical specimens

The rate of recovery and the mean time to detection of mycobacteria in clin ical specimens were evaluated with two nonradiometric broth-based systems, the Mycobacteria Growth Indicator Tube (MGIT) and MB Redox systems. The dat a obtained for each system were compared with each other and with those obt ained with the Lowenstein-Jensen (:LJ) and Middtebrook 7H11 reference media . A total of 117 mycobacterial isolates (Mycobacterium tuberculosis, n = 11 2; nontuberculous mycobacteria, rr = 5) n ere detected in 486 clinical spec imens. The recovery rates for M. tuberculosis were 91 of 112 (81.3%) isolat es with MGIT and 81 of 112 (72.3%) isolates with MB Redox. The combination of MGIT plus MB Redox recovered 106 of the 112 (92.9%) M. tuberculosis isol ates. MGIT plus LJ pins Middlebrook 7H11 recovered 106 of the 112 (92.9%) i solates, MB Redox plus LJ plus Middlebrook 7H11 recovered 99 of the 112 (88 .4%)! isolates, and II plus Middlebrook 7H11 recovered 84 of the 112 (75.0% ) isolates, The mean time to detection of, M. tuberculosis in smear-positiv e specimens was 7.2 days with MGIT, 6.9 days with MB Redox, 20.1 days with LJ and 17.6 days with Middlebrook 7H11. The mean time to detection of M. tu berculosis in smear-negative specimens was 19.1 days with MGIT, 15.5 days w ith RIB Redox, 25.8 days with LJ, and 21.6 days with Middlebrook 7H11, The contamination rates were 4.4, 3.8, 2.1, and 2.7% for MGIT, MB Redox, LJ, an d Middlebrook 7H11, respectively. In conclusion, MGIT and MB Redox can be v iable tools in the routine mycobacteriology laboratory.