Evaluation of a commercial chemiluminescent gene probe system 'AccuProbe' for the rapid differentiation of mycobacteria, including 'MAIC X', isolated from blood and other sites, from patients with AIDS.

Optimal therapy of mycobacterial infections in acquired immunodeficiency syndrome (AIDS) is difficult to achieve because of the time needed for a conventional culture to differentiate between Mycobacterium avium-intracellulare complex (MAIC) and Mycobacterium tuberculosis complex (MTBC). The recent commercial availability of gene probing techniques has introduced the potential for more rapid differentiation. We have evaluated the suitability of this technique. The specificity of the chemiluminescent gene probe system 'AccuProbe' was determined for differentiating mycobacterial isolates from 114 AIDS patients. 'AccuProbe' was 100% specific for MTBC isolates (21 of 21 isolates). Using two separate probes to MAIC and 'M. avium-intracellulare complex subtype X' (MAIC-X), 'AccuProbe' was 96% specific (87 of 91 isolates) with 5% of isolates belonging to the MAIC-X group. There were no cross-reactions between any of the probes. Using a modification of the manufacturer's protocol, 'AccuProbe' was used in a 6-month trial for the rapid differentiation of mycobacteria grown from 'Bactec' blood culture. Fifty-seven isolates (31 patients) from 805 Bactec 13A blood cultures (510 patients) were investigated. Ninety-nine per cent of isolates were able to be identified after a mean incubation period of 2.1 weeks (SD 1.2 weeks). Ninety-three per cent of isolates were reported with a presumptive identification the same day and 99% by the day after the culture flagged positive.