Setting: Mycobacteria 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 M. tuberculosis were evaluated for their susceptibilities to isoniazid (INH), rifampicin (RIF), ethambutol (EMB) and streptomycin (SM) by MGIT and by the proportion method on Löwenstein-Jensen (L-J) medium. The concentrations of drugs in MGIT were: 0.1, 1.0, 3.5 and 0.8 microg/ml for INH, RIF, EMB and SM, respectively.
Results: The results for individual drugs showed a good correlation: the specificity 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 the accuracy values 1.0, 0.98, 0.99 and 0.91.
Conclusion: The MGIT system appears to be a reliable and simple non-radiometric method for the drug susceptibility testing of M. tuberculosis.