Antimicrobial susceptibility and MIC distribution of 41 drugs against clinical isolates from China and reference strains of nontuberculous mycobacteria

- Most NTM isolates are susceptible (S) to aminoglycosides, quinolones, three macrolides, cefmetazole, linezolid and capreomycin.
- RGM is also S to cefoxitin, clofazimine, rifapentine, doxycycline, minocycline, tigecycline, meropenem, and sulfamethoxazole.
- SGM is also S to rifabutin.
- More than 70% of Mycobacterium avium complex clinical isolates are resistant to ofloxacin and levofloxacin.
- Species-specific susceptibility suggests that it is urgent to identify NTM species and normalise treatment of NTM disease.

To treat nontuberculous mycobacteria (NTM) infections more optimally, further research pertaining to mycobacterial susceptibility to antimicrobial agents is required. A total of 82 species of NTM reference strains and 23 species of NTM clinical isolates were included. Minimum inhibitory concentrations (MICs) for 41 drugs were determined using the microdilution method in cation-adjusted Mueller-Hinton broth. The results showed that most of the NTM were susceptible to aminoglycosides, quinolones, three macrolides (clarithromycin, azithromycin and roxithromycin), cefmetazole, linezolid and capreomycin. Rapidly growing mycobacterium strains were additionally susceptible to cefoxitin, clofazimine, rifapentine, doxycycline, minocycline, tigecycline, meropenem and sulfamethoxazole, whereas slowly growing mycobacterium strains were additionally susceptible to rifabutin. This study on the susceptibility of NTM includes the largest sample size of Chinese clinical isolates and reference strains. NTM species-specific drug susceptibility patterns suggested that it is urgent to identify the species of NTM, to normalise the treatment of NTM infectious disease and to clarify the resistance mechanisms of NTM.