Detection of mycobacteria in clinical specimen using the mycobacteria growth indicator tube (MGIT) and the Lowenstein...

The recovery rates of mycobacteria strains isolated from 1200 clinical specimens using the mycobacteria growth indicator tube (MGIT) system and the conventional Lowenstein Jensen medium (LJ) were assessed. Of the 87 mycobacterial isolates recovered, 54 belonged to the M. tuberculosis complex (MTB) and 33 to the non-tuberculosis complex (NTM). MGIT recovered 78 (89.65%) mycobacteria isolates (51 MTB (94.44%) and 27 NTM (81.81%) and LJ recovered 70 (80.46%) mycobacteria isolates (49 MTB (90.74%) and 21 NTM (63.63%). Sixty one (70.1%) of the total mycobacteria isolates were recovered with both systems (46 (85.2%) MTB and 15 (45.5%) NTM). No significant difference was found between MGIT and LJ (p > 0.05) in both MTB and NTM recoveries. The average detection time for MTB was significantly shorter with MGIT than with LJ, in both the smear-positive specimens (8 vs 30 days: p < 0.0001) and smear-negative specimens (15 vs 30 days: p < 0.001). The average detection time of NTM was also shorter for MGIT (15 vs 30 days: p < 0.0001). However, the contamination rate was higher in MGIT (8.5%) than in LJ (3%). The results suggest that the use of MGIT contributes to a more rapid and effective diagnosis of mycobacterial infections particularly when combined with the classical LJ.