Nontuberculous mycobacteria (NTM) infections are increasing globally. Mycobacterium avium complex (MAC) and M. abscessus complex are the most commonly reported NTM. Oral treatment options are limited, especially for the M. abscessus. We tested delafloxacin, a new oral fluoroquinolone, against 131 isolates of NTM. Delafloxacin microdilution MICs were performed as recommended by the Clinical and Laboratory Standards Institute using cation adjusted Mueller Hinton broth. The rapidly growing m ycobacteria tested included: M. abscessus subsp. abscessus (16) and subsp. massiliense (5), M. chelonae (11), M. immunogenum (5), M. fortuitum group (13), M. porcinum (7), M. senegalense (7), M. mucogenicum group (5), and M. goodii (1). For the slowly growing NTM (SGM), M. avium (16), M. intracellulare (13), M. chimaera (9), M. arupense (5), M. simiae (5), M. lentiflavum (4), M. kansasii (6), and M. marinum (3) were tested. Delafloxacin was most active in vitro against M. fortuitum and M. mucogenicum groups and M. kansasii with MIC50 values of 0.12-0.5 μg/mL (MIC range 0.001-4 μg/mL) compared to ≤0.06->4 μg/mL for ciprofloxacin and ≤0.06->8 μg/mL for moxifloxacin. For other SGM (including MAC), and the M. abscessus/chelonae, the delafloxacin MIC range was 8->16 μg/mL compared to ciprofloxacin and moxifloxacin of 0.5->4 μg/mL and ≤0.06-8 μg/mL, respectively. To our knowledge, this is the first MIC study with delafloxacin to use Clinical and Laboratory Standards Institute (CLSI) recommended methods. This study illustrates the potential utility of delafloxacin in treatment of infections due to some NTM.
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