Objective To evaluate the reliability of BACTEC MGIT 960 in testing susceptibilities of Mycobacterium tuberculosis to 8 tuberculosis (TB) medicines for first-line and second-line treatment.
Methods The susceptibilities of 8 firstline and second-line anti-tuberculosis drugs, including isoniazid (INH), rifampicin (RFP), streptomycin (SM), ethambutol (EMB), capreomycin (CPM), kanamycin (KAN), ofloxacin (OFLX), and ethionamide (ETH), were tested by BACTEC MGIT 960 system, and the results (average time of reporting results and rater agreement) were compared with those obtained by the traditional L-J proportion method. Statistical analysis was performed using paired t test and Kappa test.
Results The agreement rates of the 4 first-line drugs, INH, RFP, SM, and EMB, tested by MGIT 960 and L-J proportion method were 98.0% (198/202), 96.5% (195/202), 94.1% (190/202), and 83.7% (169/202), respectively. The agreement rates of the 4 second-line drugs, CPM, KAN, OFLX, and ETH, were 87.0% (67/77), 93.5% (72/77), 97.4% (75/77) and 68.8% (53/77), respectively. The medians of drug susceptibility testing durations using MGIT 960 were 11 days for the first-line drugs and 8 days for the second-line drugs, respectively; while the medians using L-J proportion method were both 28 days for the first-line and the second-line drugs (P < 0.01).
Conclusion The BACTEC MGIT 960 system is an accurate and rapid method to test the susceptibilities of Mycobacterium tuberculosis to first-line and the second-line drugs, and applicable to early diagnosis and treatment of drug-resistant TB.
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