Evaluation of acridinium-ester-labeled DNA probes for identification of Mycobacterium tuberculosis and Mycobacterium avium-Mycobacterium intracellulare complex in culture.

The detectability of mycobacteria in culture by the use of nonisotopic, chemiluminescent DNA probes for Mycobacterium tuberculosis and the M. avium-M. intracellulare complex (MAC) was evaluated and compared with that by the use of 125I-labeled DNA probes for the same mycobacteria. In the assay, rRNA-directed DNA probes labeled with acridinium ester (AE-DNA probes) were used. Unhybridized probes were chemically degraded, and the esterified acridinium on the hybridized probes was hydrolyzed by the addition of alkaline hydrogen peroxide solution, resulting in the production of visible light which was measured with a luminometer. The detection limits of the AE-DNA probes were almost the same as those of the 125I-labeled DNA probes. A total of 107 clinical isolates of mycobacteria (47 isolates of M. tuberculosis, 36 MAC, and 24 atypical mycobacteria other than MAC) were tested. The sensitivity and specificity of the AE-DNA probes for M. tuberculosis were 100% both for the conventional method and with the 125I-labeled DNA probe. The sensitivity and specificity of the AE-DNA probes for MAC were 97.2 and 100%, respectively, for the conventional method and were both 100% with the 125I-labeled DNA probes. Because the procedure is simple, reliable, rapid (it can be completed within an hour), and safe (it does not use radioisotopes), it can easily be performed in any clinical laboratory.