Comparison of recovery rates for mycobacteria from BACTEC 12B vials, Middlebrook 7H11-selective 7H11 biplates, and Lowenstein Jensen slants in a public health mycobacteriology laboratory.

Recovery rates from Middlebrook 7H11-selective 7H11 biplates and Lowenstein-Jensen slants (LJ) used with BACTEC 12B vials were compared for 5,399 specimens. For 578 specimens that were inoculated onto three media, 580 mycobacteria were isolated, including 277 (48%) Mycobacterium avium complex isolates, 230 (40%) Mycobacterium tuberculosis isolates, and 73 (12%) other mycobacteria. For BACTEC 12B vials, 506 (87%) cultures were positive, 45 (8%) were negative, and 29 (5%) were lost to contamination; for 7H11-7H11-selective biplates, 469 (81%) cultures were positive, 95 (16%) were negative, and 16 (3%) were lost to contamination; for LJ, 230 (40%) cultures were positive, 111 (19%) were negative, and 239 (41%) were lost to contamination. For routine cultures, use of plate media is superior to use of LJ.