Multicenter evaluation of the BACTEC MGIT 960 system for recovery of mycobacteria

We evaluated the BACTEC MGIT 960 system, which is a fully automated, noninv asive system for the growth and detection of mycobacteria with a capacity t o incubate and continuously monitor 960 7-ml culture tubes, We studied 3,33 0 specimens, 2,210 respiratory and 1,120 nonrespiratory; specimens, collect ed from 2,346 patients treated at six sites. Processed specimens were inocu lated into the BACTEC MGIT 960 and BACTEC 460 TB systems, as well as onto L owenstein-Jensen slants and Middlebrook 7H11/7H11 selective plates, From al l culture systems, a total of 362 isolates of mycobacteria Here recovered; these were recovered from 353 specimens collected from 247 patients, The gr eatest number of isolates of mycobacteria (289, or 80% of the 362 isolates) was recovered with the BACTEC MGIT 960, followed by the BACTEC 460 TB (271 , or 75%) and solid media (250, or 69%). From all culture systems a total o f 132 isolates of Mycobacterium tuberculosis complex, were recovered. The g reatest number of isolates of M. tuberculosis complex was recovered when li quid medium was combined with conventional solid media; the number recovere d with BACTEC 460 TB plus solid media was 128 (97%), that recovered with BA CTEC MGIT 960 plus solid media was 121 (92%), that recovered with BACTEC 46 0 TB was 119 (90%) and that recovered with all solid media combined Has 105 (79%). The recovery with BACTEC MGIT 960 alone Has 102 (77%). The mean tim es to detection (TTD) for, M. tuberculosis complex I Here 14.4 days for BAC TEC MGIT, 15.2 days for BACTEC 460 TBI and 24.1 days for solid media. The n umbers of isolates of Mycobacterium al avium complex (,MAC) recovered were 172 (100%) for all systems, 147 (85%) for BACTEC MGIT 960, 123 (72%) for BA CTEC 460 TB, and 106 (62%) for all solid media combined. The TTD for MAC in each system were 10.0 days for BACTEC MGIT 960, 10.4 days for BACTEC 460 T B, and 25.9 days for solid media, Breakthrough contamination rates (percent ages of isolates) for each of the systems were 8.1% for BACTEC MGIT 960, 4. 9% for BACTEC 460 TB, and 21.1% for all solid media combined.