Differences in risk factors and drug susceptibility between Mycobacterium avium and Mycobacterium intracellulare lung diseases in China.

The aim of this study was to investigate the differences in risk factors and drug susceptibility between Mycobacterium avium and Mycobacterium intracellulare lung diseases in China. In total, 452 nontuberculous mycobacteria (NTM) strains isolated from patients with NTM lung diseases in four specialised TB hospitals were enrolled in this study. The minimum inhibitory concentration (MIC) was used to evaluate the drug susceptibility of M. avium and M. intracellulare isolates. In addition, demographic and clinical characteristics of patients with NTM lung diseases caused by M. avium and M. intracellulare were analysed. Of 452 NTM isolates, M. intracellulare (188; 41.6%) was the most frequently isolated organism. The percentages of moxifloxacin- and linezolid-resistant strains among the M. intracellulare isolates were significantly lower than those among the M. avium group (P=0.003 and P<0.001, respectively). In contrast, M. avium harboured a lower proportion of rifampicin-resistant strains than M. intracellulare (P=0.005). Among patients with M. intracellulare lung diseases, the percentages of patients aged >64 years and patients with chronic obstructive pulmonary disease (COPD) were significantly higher than among patients with M. avium (P=0.008 for age and P=0.001 for COPD). In conclusion, these data demonstrated that M. intracellulare was the most common NTM species in China. This study also revealed that M. intracellulare and M. avium differed in their drug susceptibility profiles. In addition, clinical cases of M. intracellulare lung diseases were more likely to be found in the aged population and among patients with COPD co-morbidity.