In vitro susceptibility testing of bedaquiline against mycobacteria avium-intracellulare complex

Introduction: Infections caused by non-tuberculous mycobacteria (NTM) have become more frequent in the last years. Their treatment is long-lasting, toxic, and often with poor results due to the natural resistance of NTM to many antibacterial drugs (ABD). Mycobacteria avium-intracellulare complex (MAC) are the most common pathogens of mycobacteriosis and are more resistant to ABD than other types of NTM. Bedaquiline (BDQ) has recently been used for the treatment of multidrug-resistant tuberculosis and there is increasing interest in its potential use for treating MAC infections The aim of this study was to evaluate the in vitro activity of bedaquiline against mycobacteria avium-intracellulare complex. Materials and Methods: We studied 81 strains MAC (50 M. avium and 31 M. intracellulare) obtained from 81 patients admitted to MRCCTC for diagnosis and treatment. The minimal inhibitory concentrations (MIC) was determined by the broth microdilution method in Middlebrook 7H9 medium supplemented with OADC. Range concentration of BDQ was assessed from 0.06 to 2.0 μg/ml. Results: For the majority of M. avium (92%) and M. intracellulare (93.5%) isolates, MICs of BDQ were established in the range of 0.06-0.25 µg/ml. 4 (8.0%) strains of M. avium and 2 (6.5%) of M. intracellulare were inhibited BDQ concentrations from 0.5 to 2.0 µg/ml. MIC 50 and MIC 90 of bedaquiline were the same and amounted to 0.12 µg/ml and 0.25 mcg/ml, for M. avium and M. intracellulare respectively. Conclusion: It was found that bedaquiline has activity against MAC, which makes it potentially possible to use it in treatment regimens for infections caused by this pathogen.