Identification of Mycobacterium avium complex strains belonging to serovars 21-28 by three commercial DNA probe tests

Various reference strains of Mycobacterium avium complex (MAC) belonging to serovars 21-28 were identified by three DNA probe tests, i.e., Gen-Probe, AccuProbe and SNAP tests. All of these DNA probe tests were in agreement for strains identified as M. avium or M. intracellulare. The tested serovar strains involved M. avium, M. intracellulare, MAC reactive only with Probe X of SNAP test ('Probe X-reactive MAC'), M. scrofulaceum reactive with Probe X of SNAP test ('Probe X-reactive M. scrofulaceum'), and typical M. scrofulaceum which did not react with any of the probes. Both reference strains belonging to serovar 21 were M. avium, and none of the other serovars included this species. On the contrary, M. intracellulare was found in serovars 22, 25, 26, and 28. 'Probe X-reactive MAC' were also widely found in serovars 23, 24, 26, 27, and 28, while 'Probe X-reactive M. scrofulaceum' was seen only in serovar 22. These results confirm the usefulness of SNAP test to identify the MAC showing no reactivity to Gen-Probe and AccuProbe.