Multicenter Research on the BACTEC MGIT 960 system for the second-line drugs susceptibility testing of Mycobacterium tuberculosis in China

The reliability of the BACTEC MGIT 960 system for the second-line drugs (capreomycin [CPM], kanamycin [KAN], ofloxacin [OFX] and ethionamide [ETH]) susceptibility testing (DST) of Mycobacterium tuberculosis (M. tuberculosis) was compared to that of traditional Lowenstein-Jensen (L-J) proportion method (PM) among four different sites in China. After resolution of discrepant results by retesting the strains using both methods in the National Reference Laboratory of tuberculosis, the overall concordance values between the 2 systems were 99.7% (kappa value: 0.97) for CPM, 99.7% (kappa value: 0.97) for KAN, 100.0% (kappa value: 1.00) for OFX, and 98.6% (kappa value: 0.95) for ETH. The average turnaround time with BACTEC MGIT 960 system among four sites was 8.9 ± 1.7 days, significantly shorter than 28 days with the traditional L-J PM. Therefore, the BACTEC MGIT 960 system is a reliable and rapid method for the second-line drug susceptibility testing of tuberculosis in China. Notably, a stricter quality control program should be routinely carried out when clinical laboratories perform the second-line DST with BACTEC MGIT 960 system.