In Vitro Susceptibility Testing of Tedizolid against Nontuberculous Mycobacteria

Abstract

ABSTRACT Tedizolid is a new oxazolidinone with improved in vitro and intracellular potency against Mycobacterium tuberculosis , including multidrug-resistant strains, and some species of nontuberculous mycobacteria (NTM) compared with that of linezolid. Using the current Clinical and Laboratory Standards Institute (CLSI)-recommended method of broth microdilution, susceptibility testing of 170 isolates of rapidly growing mycobacteria showed equivalent or lower (1- to 8-fold) MIC 50 and/or MIC 90 values for tedizolid compared with that for linezolid. The tedizolid MIC 90 values for 81 isolates of M. abscessus subsp. abscessus and 12 isolates of M. abscessus subsp. massiliense were 8 μg/ml and 4 μg/ml, respectively, compared with linezolid MIC 90 values of 32 μg/ml for both. The MIC 90 values for 20 isolates of M. fortuitum were 2 μg/ml for tedizolid and 4 μg/ml for linezolid. Twenty-two isolates of M. chelonae had tedizolid and linezolid MIC 90 s of 2 μg/ml and 16 μg/ml, respectively. One hundred forty-two slowly growing NTM, including 7/7 M. marinum , 7/7 M. kansasii , and 7/11 of other less commonly isolated species, had tedizolid MICs of ≤1 μg/ml and linezolid MICs of ≤4 μg/ml. One hundred isolates of Mycobacterium avium complex and eight M. simiae isolates had tedizolid MIC 50 s of 8 μg/ml and linezolid MIC 50 s 32 and 64 μg/ml, respectively. Nine M. arupense isolates had MIC 50 s of 4 μg/ml and 16 μg/ml for tedizolid and linezolid, respectively. These findings demonstrate a greater in vitro potency of tedizolid than linezolid against NTM and suggest that an evaluation of tedizolid as a potential treatment agent for infections caused by selected NTM is warranted.