Conventional identification characteristics, mycolate and fatty acid composition, and clinical significance of MAIX AccuProbe-positive isolates of Mycobacterium avium complex.

A total of 145 isolates belonging to the Mycobacterium avium complex (MAC) were tested with commercial acridinium ester-labeled DNA probes (AccuProbe, Gen-Probe). M. avium and M. intracellulare probes reacted with 102 and 36 isolates, respectively. The remaining seven isolates were clearly positive with the new probe, designated MAIX. Thus, the combined sensitivity of M. avium and M. intracellulare probes was 95.2%. The MAIX probe improved the sensitivity up to 100%. The MAIX probe also reacted with all M. avium (n = 20) and M. intracellulare (n = 20) isolates tested. Three of the seven MAIX-positive isolates were considered clinically significant. We conclude that the new MAIX probe should be used, in addition to M. avium and M. intracellulare probes, for the identification of MAC isolates. Our results also suggest that the probe may be used alone to cover the whole MAC when species differentiation is not required.