[Identification of Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium tuberculosis complex by...

DNA probe testing for Mycobacterium avium, Mycobacterium intracellulare and Mycobacterium tuberculosis complex (MTC) was performed using Gen-Probe Rapid Diagnostic System (Gen-Probe Inc., San Diego, Calif., U.S.A.). By DNA probe test carried out blindfold for 48 mycobacterial strains with code numbers obtained from Kyoto University (Prof. F. Kuze), 13, 7, and 5 strains were identified as to be M. avium, M. intracellulare, and MTC, respectively. The diagnostic specificity and sensitivity of this testing were 100%. In this experiment, % hybridization of M. avium complex (MAC) and MTC were 25-55% and 45-52%, respectively. DNA probe test for 54 MTC strains including M. tuberculosis, M. bovis, M. africanum and M. microti revealed that 53 strains, except for one strain donated as a niacin-negative M. tuberculosis, reacted with MTC probe but not with MAC-probes. The one exceptional strain reacted with both the MTC- and M. avium-probes. However, when ten colonies randomly isolated from this strain on 7H11 agar plate were subjected to the DNA probe test again, all of these colonies reacted with M. avium probe, but not with MTC probe. Moreover, one representative colony was found to have alpha-antigen specific for the MAC.