Determination of MIC Distribution and Epidemiological Cutoff Values for Bedaquiline and Delamanid in Mycobacterium tuberculosis Using the MGIT 960 System Equipped with TB eXiST

Bedaquiline (Sirturo) and delamanid (Deltyba) have recently been approved by the regulatory authorities for treatment of multidrug-resistant tuberculosis (MDR-TB). Antimicrobial susceptibility testing is not established for either substance. On the basis of the use of the MGIT 960 system equipped with EpiCenter/TB eXiST, we determined a mean bedaquiline MIC for wild-type strains of 0.65 mg/liter (median, 0.4 mg/liter) and an epidemiological cutoff (ECOFF) of 1.6 mg/liter; for delamanid, a mean wild-type drug MIC of 0.013 mg/liter (median, 0.01 mg/liter) and an ECOFF of 0.04 mg/liter were determined.