F. Ardito et al., Evaluation of BACTEC mycobacteria growth indicator tube (MGIT 960) automated system for drug susceptibility testing of Mycobacterium tuberculosis, J CLIN MICR, 39(12), 2001, pp. 4440-4444
The reliability of the BACTEC MGIT 960 system, an automated version of the
Mycobacteria Growth Indicator Tube (MGIT), for antimicrobial susceptibility
testing of Mycobacterium tuberculosis was evaluated on 78 clinical isolate
s. Rifampin (RMP), isoniazid (INH), streptomycin (SM), and ethambutol (EMB)
were tested at the following concentrations: 1.0 mug/ml for RMP, 0.1 and 0
.4 mug/ml for INH, 1.0 and 4.0 mug/ml for SM, and 5.0 and 7.5 mug/ml for EM
B. Results were compared with those obtained by the BACTEC 460 TB radiometr
ic system. Initially the reproducibility study showed 99.5% agreement on re
peat testing with all the four drugs. With susceptibility testing of clinic
al isolates, excellent agreement between the two systems was found for all
the drugs. A total of nine major errors were observed for only three isolat
es, resistant according to BACTEC MGIT 960 and susceptible according to BAC
TEC 460 TB, to SM (4.0 mug/ml), INH (0.1 mug/ml), and EMB (5.0 mug/ml) (one
isolate) and to SM (1.0 mug/ml), INH (0.4 mug/ml), and EMB (5.0 mug/ml) (t
wo isolates). When these isolates were tested by using the conventional pro
portion method on Lowenstein-Jensen medium, agreement with BACTEC MGIT 960
was found for five results and with BACTEC 460 TB for the remainder. The ti
me to report results was 7.9 days by MGIT 960 and 7.3 days by BACTEC 460 TB
, which was not found statistically significant (P > 0.05). In conclusion,
the performance of BACTEC MGIT 960 was found similar to that of BACTEC 460
TB and this new system can be considered a good alternative to the radiomet
ric method for routine susceptibility testing of M. tuberculosis.