Comparison of the mycobacteria growth indicator tube with radiometric and solid culture for isolation of mycobacteria from clinical specimens and susceptibility testing of Mycobacterium tuberculosis

We compared the mycobacteria growth indicator tube (MGIT) system with the B ACTEC 460 TB and Loewenstein-Jensen (LJ) systems for the recovery of mycoba cteria (acid-fast bacilli [AFB]) from 600 clinical specimens. A total of 50 AFB (32 Mycobacterium tuberculosis complex, 10 M. avium complex, 3 M. gord onae, 3 M. xenopi, 1 M. terrae and 1 M. fortuitum) were detected. MGIT reco vered 50 isolates of AFB (100% sensitivity), and BACTEC 460 TB and LJ recov ered 49 (98% sensitivity) and 19 (38% sensitivity) AFB isolates, respective ly. The mean times to detect mycobacteria were 10, 10 and 25 days for MGIT, BACTEC 460, and LJ slants. All isolates of M. tuberculosis complex were te sted for susceptibility to streptomycin, isoniazid, rifampin, and ethambuto l with the MGIT and BACTEC 460 TB. Both systems yielded identical susceptib ility data with different mean times to report (5.38 days for MGIT versus 7 .33 days for BACTEC 460 TB, P<0.05). The results suggest that MGIT is equiv alent to BACTEC 460 TB in its ability to support the growth of mycobacteria , but significantly more efficient than LJ. MGIT may also be used for susce ptibility testing of primary antituberculosis drugs.