Evaluation of Mycobacteria Growth Indicator Tube (MGIT) for drug susceptibility testing of Mycobacterium tuberculosis

SETTING: Mycobactoria Supranational Reference Laboratory. OBJECTIVE: To evaluate the Mycobacteria Growth Indicator Tube (MGIT) method for drug susceptibility testing of Mycobacterium tuberculosis. DESIGN: One hundred and one clinical strains of hi. tuberculosis were evalu ated for their susceptibilities to isoniazid (INH), rifampicin (RIF), etham butol (EMB) and streptomycin (SM) by MGIT and by the proportion method on L owenstein-Jensen (L-J) medium. The concentrations of drugs in MGIT were: 0. 1, 1.0, 3.5 and 0.8 mu g/ml for INH, RIF, EMB and SM, respectively. RESULTS: The results for individual drugs showed a good correlation: the sp ecificity was 100% for INH, RIF and EMB and 92% for SM; the sensitivity was 100%, 94.6%, 96.1% and 89.7% for INH, RIF EMB and SM, respectively, and th e accuracy values 1.0, 0.98, 0.99 and 0.91. CONCLUSION: The MGIT system appears to be a reliable and simple non-radiome tric method for the drug susceptibility testing of RI. tuberculosis.