Evaluation of the MB/BACT automated mycobacteria culture system versus culture on Lowenstein medium

To evaluate the growth time and recovery rate of mycobacteria, and the percentage of contamination in the MB/BACT system versus traditional culture, on Lowenstein medium. One thousand one hundred and fifty-nine samples for mycobacterial analysis were cultured in Lowenstein medium and the MB/BACT system: 0.5-mL aliquots of the sample were inoculated into tubes containing either medium and incubated for 49 days. The mycobacterial isolates were identified by means of the Accu-Probe (Gen-Probe) or a system based on chromogenesis, time and temperature of growth and principal biochemical differentiation analyses. Fischer's test was performed. Ninety-three mycobacterial strains were isolated: 80 Mycobacterium tuberculosis, seven strains of the M. avlum-intracellulare complex, four M. gordonae and two M. smegmatis. For M. tuberculosis, 76 of 80 isolates grew in MB/BACT, while 60 of 80 grew on Lowenstein medium. A total of 88 of the mycobacterial strains grew in the MB/BACT system, while 66 grew on the Lowenstein solid medium. Growth in the MB/BACT averaged 16.51 days, as opposed to 22.71 days on Lowenstein medium. The MB/BACT system is a suitable complement to culturing on Lowenstein medium, while the workload does not significantly increase in comparison with culturing on solid media only and still allows major recovery of mycobacteria with a significant time-saving.