[Rapid detection of acid-fast bacilli with Mycobacteria Growth Indicator Tube (MGIT)]

The BBL MGIT Mycobacteria Growth Indicator Tube is a novel broth based culture system for the detection of mycobacteria from clinical specimens. The tubes consist of a fluorescent indicator embedded in silicone on the bottom of a 16x100 mm round-bottom tube, filled with 4ml of an enriched BBL Middlebrook 7H9 broth base, with 0.25% glycerol. Actively growing mycobacteria consume the oxygen dissolved in the medium and fluorescence will occur when the tubes are observed with a 365nm transilluminator. The purpose of this study is to evaluate comparatively MGIT with 1% Ogawa egg medium by using two hundred and forty-five clinical specimens. The samples were digested, decontaminated and concentrated for culture using N-acetyl-L-cysteine-sodium hydroxide method. Fifty-nine of 245 (24%) clinical samples were culture positive for mycobacteria (43 M. tuberculosis complex, 12 M. avium complex and 4 other species) by one or both test systems. The MGIT detected 4 isolates of M. tuberculosis complex and 6 isolates of M. avium complex not recovered by the Ogawa egg medium, respectively. The mean time of detection of M. tuberculosis complex was 13 days (range: 2-26 days) and 19 days (range: 8-31 days) for MGIT and Ogawa egg medium, respectively, and that of M. avium complex was 5 days (range: 2-8 days) and 16 days (range: 6-22 days) for the MGIT and Ogawa egg medium, respectively. Overall, the MGIT is a sensitive culture system for the detection of mycobacteria from clinical specimens, is easy to use and may be applicable to clinical laboratories.