Optimum recovery of Mycobacterium avium complex from blood specimens of human immunodeficiency virus-positive patients by using small volumes of isolator concentrate inoculated into BACTEC 12B bottles.

Recovery of Mycobacterium avium complex organisms from 412 lysis-centrifugation (Isolator) concentrates of blood specimens obtained from human immunodeficiency virus-positive individuals was attempted with the following media (and Isolator concentrate inoculum volumes): BACTEC 12B broth (0.2 and 1.0 ml), Lowenstein-Jensen slants (0.1 ml), and Middlebrook 7H10/11 agar (0.1 ml). A total of 42 M. avium complex isolates were recovered. The highest rates of recovery and shortest detection times were noted with BACTEC 12B bottles inoculated with 0.2 ml of Isolator concentrate. Middlebrook agar was superior to Lowenstein-Jensen slants. Fluorochrome acid-fast smears performed directly upon Isolator concentrates were of no utility.