Rapid identification using a specific DNA probe of Mycobacterium avium complex from patients with acquired...

Specific DNA probes (Gen-Probe Corp., San Diego, Calif.) for Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium tuberculosis were compared with conventional methods for the identification of isolates of the Mycobacterium avium complex. A total of 56 isolates of M. avium complex were recovered from 34 respiratory, 13 blood, 6 stool, and 3 urine samples from 23 patients. A total of 33 isolates were tested directly from Middlebrook 7H11 agar plates, and 23 isolates were tested directly from BACTEC radiometric 12B bottles (Johnston Laboratories, Inc., Towson, Md.). Of the 56 M. avium complex isolates, 41 tested positive with the M. avium probe, 4 were positive with the M. intracellulare probe, and 7 were positive with both probes. Four direct tests from BACTEC bottles were initially negative but were subsequently M. avium probe positive when subcultures from Lowenstein-Jensen agar were tested. All 56 strains were negative when tested with the M. tuberculosis probe.