Comparison of recoveries of Mycobacterium tuberculosis using the automated BACTEC MGIT 960 System and Lowenstein – Jensen medium

We examined whether the BACTEC/Mycobacxteria Growth Indicator Tube (MGIT) System alone could supplant the use of a supplemental Lowenstein–Jensen (LJ) slant for routine recovery of M. tuberculosis from clinical specimens . A total of 392 specimens of sputum were included in the study , collected from 196 patients . Specimens were processed with standard N-acetylLCysteine (NALC-NaOH) method , then inoculated onto BACTEC MGIT 960 and onto LJ media.The recovery rates of M.tuberculosis were 100 % (256/256) with BACTEC MGIT 960 and 72.6%(186/256) with LJ . The rates of contamination for each of the system were 4.8%with BACTEC MGIT 960 and 5.3%with LJ.The TTD for M. tuberculosis were 11.3 days with BACTEC System and 30.8 days with LJ.The difference in TTD between smear positive and smear negative specimens for M.tuberculosis with BACTEC MGIT 960 was not statistically significant.This study shows that the BACTEC System demonstrates better sensitivity for the recovery of M. tuberculosis from clinical specimens.