Evaluation of the mycobacteria growth indicator tube compared to Septi-Chek AFB for the detection of mycobacteria.

The Mycobacteria Growth Indicator Tube (MGIT) and the AFB Septi-Check (SC) systems were compared for the ability to detect myobacterial isolates, time to detection, and rate of bacterial contamination. Fifty-eight mycobacterial culture positive specimens were studied. MGIT and SC were both positive in 30 of the 58 specimens (52%); SC alone was positive in 22 (38%), and MGIT alone was positive in 6 (10%) of the 58 specimens. Among the 30 isolates identified in both systems, there were 7 Mycobacterium tuberculosis, 14 M. avium, 6 M. fortuitum-chelonae complex, and 3 other mycobacterial species. MGIT detected Mycobacterium tuberculosis faster; SC detected M. avium complex faster and more often; and M. fortuitum-chelonae isolates were detected at the same rate. MGIT showed more contamination (12.6%) than did the SC (7.8%). MGIT is comparable to SC for the detection of MTB, but MAC isolates were detected more often and faster in the SC system.