Rapid testing for nitrate reductase activity of Mycobacterium tuberculosis grown in an automated culture system

In order to reduce the time to detection of nitrate reductase activity, which is arguably the most widely used phenotypic trait to differentiate between Mycobacterium tuberculosis, Mycobacterium bovis and Mycobacterium bovis BCG, the following study was conducted using cultures grown in an automated system. Automated culture systems, which are typically based on liquid medium, have greatly reduced the time-to-recovery of mycobacteria. Yet subsequent testing of isolates for nitrate reductase activity may take several weeks, because culture on solid media is required. Presented here is a procedure to obtain a final result within 24 h for nitrate reductase activity of cultures grown in an automated culture system. Using this procedure, Mycobacterium tuberculosis was rapidly differentiated from Mycobacterium bovis and Mycobacterium bovis BCG.