Improved detection of Mycobacterium spp. using the Bactec MGIT 960 system

Until 1987, the notification rate for mycobacterial infection was on the decline; however, it now appears to be increasing once more. The reason for this may be multifactoral and include improved reporting of diagnosed cases, increased infection of an ageing population, homelessness, immunosuppression (e.g. due to human immunodeficiency virus infection), and immigration of people from countries where tuberculosis is endemic. This rising incidence and the increasing importance of resistant organisms mean that rapid identification by the clinical microbiology laboratory is required, and this is where an automated detection system can be an advantage. Over a two-year period, 2743 clinical specimen were examined for Mycobacterium spp. using the Bactec MGIT 960, and 286 were positive. Time to detection ranged from three to 14 days (mean: 9.3 days), and M. tuberculosis was recovered from 214 (75.5%). Contamination rate was higher (8.6%) than with manual methods, however. On balance, the Bactec MGIT 960 system proved a valuable tool in the routine microbiology laboratory.