activity of fidaxomicin against nontuberculosis mycobacteria.

Nontuberculous mycobacteria (NTM) infections are increasing worldwide and are relatively resistant to many of the first- and second-line drugs to treat tuberculosis. Macrolide antibiotics, such as clarithromycin and azithromycin, are the key drugs for treating NTM infections. Fidaxomicin is a macrolide antibiotic that is widely used in treating infections, and has high activity against especially multidrug-resistant tuberculosis (MDR-TB) and has no cross-resistance with rifampicin. Fidaxomicin may have activity against NTM strains. To find that whether the macrolide antibiotic fidaxomicin has activity against NTM strains. Fidaxomicin used in this study was firstly tested on reference strains and has shown to be effective and workable. And then 28 rapidly growing mycobacteria (RGM), 12 slowly growing mycobacteria (SGM) reference strains and 103 NTM clinical isolates were tested by the microplate-based AlamarBlue assay (MABA) method to determine the MICs. Fidaxomicin, rifampicin and clarithromycin were tested against omplex subspecies 14 . and 5 . strains for inducible resistance determination. In total, 21 out of 28 RGM and 9 of 12 SGM reference strains have the MICs of fidaxomicin at or below 1 µg ml. Fidaxomicin also showed low MIC values for some clinical isolates including complex, complex, , and . Fidaxomicin also has no inducible macrolide resistance in complex in comparison with clarithromycin. Fidaxomicin has high activity against most of the NTM reference strains and some prevalent NTM clinical isolates. This promising finding warrants further investigation on the actions of fidaxomicn and as a potential antibiotic for NTM treatment.