Comparison of the MB/BacT and BACTEC 460 TB systems for recovery of mycobacteria from various clinical specimens

A total of 1,830 specimens (75.7% respiratory and 24.3% nonrespiratory) wer e cultured in parallel with the MB/BacT and BACTEC 460 TB systems and on Lo wenstein-Jensen (LJ) medium. Mycobacteria were identified from 173 (6.5%) s pecimens. The most common species recovered were Mycobacterium tuberculosis complex (65.9%), Mycobacterium avium complex (22.5%), and Mycobacterium ch elonac (9.2%), The recovery rates by individual systems were 96.5, 99.4, an d 95.9% for MB/BacT, BACTEC 460 TB, and LJ medium, respectively, for all my cobacteria; the recovery rates were 99.1, 100, and 98.2%, respectively, for M. tuberculosis complex alone. The difference among the recovery rates for all mycobacteria and those for individual species was not significant. The BACTEC 460 TB system detected M. tuberculosis isolates more rapidly than t he MB/BacT system (8 versus 11.8 days for smear-positive specimens [P < 0.0 1] and 18 versus 21 days for smear-negative specimens [P < 0.05]), whereas the MB/BacT system more rapidly detected the nontuberculous mycobacteria (1 7.1 versus 12.7 days [P < 0.01]). These results indicate that the nonradiom etric MB/BacT system is a rapid, sensitive, and efficient method for the re covery of M. tuberculosis and nontuberculous mycobacteria from both pulmona ry and extrapulmonary clinical specimens.