Susceptibility of the nontuberculous mycobacteria circulating in Russia to bedaquiline

The diseases caused by nontuberculous mycobacteria (NTM) are a public health problem all over the world due to increasing incidence and the associated mortality. Since it is difficult to treat mycobacteriosis, the search for drugs effective against NTM is relevant. Bedaquiline was approved in 2012 as a drug for tuberculosis treatment. The study aimed to determine susceptibility to bedaquiline of the main clinically significant NTM species that were common in the Russian Federation. In 2011–2024, a total of 345 NTM isolates were obtained: 289 isolates of slow growing NTM species (M. avium, M. intracellulare, M. chimaera, M. kansasii, M. xenopi) and 56 of the fast growing one (M. abscessus). Drug susceptibility testing for bedaquiline was performed by microdilution in a 96-well plate using the bedaquiline concentration range of 0.125–4 µg/mL. The minimum inhibitory concentration of bedaquiline inhibiting 50% (MIC50) and 90% (MIC90) of NTM strains of each spesies was determined. It has been shown that the bedaquiline MIC50 for M. avium, M. intracellulare, M. chimaera, M. kansasii is < 0.125 µg/mL, MIC90 — from < 0.125 to 0.5 µg/mL, for M. xenopi: MIC50 —4 µg/mL, MIC90 — > 4 µg/mL, M. abscessus: MIC50 — 1 µg/mL, MIC90 — 2 µg/mL.