Rapid identification of mycobacteria by the Gen-Probe Accuprobe system

Chemiluminescent acridinium ester-labelled (AE)-DNA probes (Gen-Probe, Inc., San Diego, Calif.) for the identification of Mycobacterium tuberculosis complex (MTBC) and the M. avium-M. intracellulare complex (MAC) were evaluated using 184 mycobacterial isolates cultured in BACTEC 12B vials (Becton Dickinson and Co., Towson, Md.). A 1.5 mL aliquot from BACTEC 12B vials containing acid-fast bacilli and a Growth Index of > 200 was concentrated 15-fold using a centrifugation step prior to performing the test procedure. When 184 mycobacterial isolates were tested (42MTBC/142 nontuberculous mycobacteria) using the AE-MTBC probe, there was 100% sensitivity and specificity when compared with conventional identification procedures. Criteria for using the AE-MAC probe were defined to optimize results whilst minimizing laboratory costs. Ninety-one (64%) of AE-MTBC probe negative isolates failed to meet selection criteria and were not tested. When 51 (36%) of the AE-MTBC-probe negative mycobacterial isolates were tested, the AE-MAC probe was found to be 88% sensitive and 100% specific. The non-isotopic Gen-Probe test is a rapid and practical alternative to current procedures for differentiation of mycobacteria.