We have evaluated the efficiency of the TK Rapid Mycobacterial Culture System in isolating mycobacteria from clinical samples and in susceptibility testing. The TK Medium indicates mycobacterial growth by changing its color from red to yellow. During a 1-year period, 16,303 clinical samples were inoculated to TK selective (TK SLC) and Lowenstein-Jensen media (LJ). Mycobacteria were isolated in 2150 (13.04%) samples in at least 1 type of medium. While U isolated mycobacteria from 1920(11.69%) of all samples, TK SLC isolated 2070 (12.63%). Among all positives, the isolation rates for U and TK SLC were 89.30% and 96.27%, respectively. Contamination of cultures by other organisms was observed in 878 (5.33%) LJ tubes and in 90 (0.55%) TK SLC tubes. On average, time-to-growth detection was 15.57 days in TK SLC and 25.14 days in U. The modes of time-to-growth detection were 12 and 25 days for TK SLC and LJ, respectively. The reliability of antimycobacterial susceptibility testing was checked by 36 Mycobacterium tuberculosis strains with known susceptibility patterns which were obtained from the World Health Organization collection and by participating in an external quality control program. All susceptibility results, except for a few borderline-resistant strains, were consistent with the expected susceptibility patterns. The TK Rapid Mycobacterial Culture System is a practical and reliable automated system that shortens the time required for both culture and susceptibility results. All types of TK Media are ready to use, saving time and effort as well as drastically reducing contamination during testing. (C) 2012 Elsevier Inc. All rights reserved.