Drug Susceptibility Distributions of Mycobacterium chimaera and Other Nontuberculous Mycobacteria

Recent outbreaks of cardiac surgery-associated Mycobacterium chimaera infections have highlighted the importance of species differentiation within the Mycobacterium avium complex and pointed to a lack of antibiotic susceptibility data for M. chimaera Using the MGIT 960/EpiCenter TB eXiST platform, we have determined antibiotic susceptibility patterns of 48 clinical M. chimaera isolates and 139 other non-tuberculous mycobacteria including 119 members of the M. avium complex and 20 Mycobacterium kansasii towards clofazimine and other drugs used to treat infections with slowly growing nontuberculous mycobacteria (NTM). MIC50, MIC90 and tentative epidemiological cutoff (ECOFF) values for clofazimine were 0.5 mg/L, 1 mg/L and 2 mg/L for M. chimaera. Comparable values were observed for other M. avium complex members, lower MIC50 (≤0.25 mg/L), MIC90 (0.5 mg/L) and ECOFF (1 mg/L) values were found for M. kansasii Susceptibility to clarithromycin, ethambutol, rifampin, rifabutin, amikacin, moxifloxacin and linezolid was in general similar for M. chimaera and other members of the M. avium complex but increased for M. kansasii The herein determined MIC distributions, MIC90 and ECOFF values of clofazimine for M.chimaera and other NTM provide the basis for the definition of clinical breakpoints. Further studies are needed to establish correlation of in vitro susceptibility and clinical outcome.