Identification and partial characterization of Mycobacterium avium and Mycobacterium intracellulare by using DNA probes.

We attempted to identify the Mycobacterium avium complex (MAC) isolated in Japan by using DNA probes specific for M. avium or Mycobacterium intracellulare (Gen-Probe Rapid Diagnostic System for MAC; Gen-Probe, Inc., San Diego, Calif.). The source and drug susceptibility distributions were examined. This assay system proved to be rapid, sensitive, specific, and reliable for identification of MAC and of the species as either M. avium or M. intracellulare. The DNA probe test showed that of the generally accepted MAC serovars, serovars 1 to 6, 8 to 11, and 21 belonged to M. avium and 7 and 12 to 20 belonged to M. intracellulare. Moreover, with the DNA probe test we found that the distribution patterns of M. avium and M. intracellulare isolates in Japan differed depending on the district in which MAC was isolated. The ratio of M. avium was much higher in eastern Japan. In Tokai and Shimane districts, the ratio of M. avium and M. intracellulare isolates significant in human disease was related to that of isolates from soil and house dust (natural sources). In M. avium, human disease-associated isolates were more resistant to rifampin, streptomycin, and kanamycin than were isolates from natural sources. However, this source dependence was not evident for M. intracellulare. In human disease-associated MAC, M. avium isolates were more resistant to most agents, except for quinolones, than were M. intracellulare isolates.