[Evaluation of the Mycobacteria Growth Indicator Tube system for detection and quantification of mycobacteria from...

The Mycobacteria Growth Indicator Tube (MGIT) system, a broth system for detection of mycobacterial growth, has been shown to be more sensitive and rapid compared with the egg-based Ogawa solid media, while the lack of ability to quantitate bacterial growth is the problem. We compared mycobacterial growth in the MGIT and the Ogawa systems, and evaluated the relationship between detection time in the MGIT system and bacterial CFU on Ogawa egg medium. A total of 413 respiratory specimens from 245 patients were included in the study, of which Mycobacterium tuberculosis (MTB), M. avium complex (MAC) and M. kansasii were recovered from 127, 42 and 6 specimens, respectively. Recovery rates were significantly higher and detection time was significantly shorter in the MGIT than in the Ogawa for MTB and MAC. Detection time in the MGIT was significantly shorter in smear positive specimens than in smear negative ones for MTB and MAC. There was a significant negative correlation between CFUs on Ogawa egg medium and detection time in the MGIT system for the MTB, therefore, this system may have an ability to quantitate live mycobacteria according to the detection time.