Isolation Rate and Species Distribution of Non-Tuberculous Mycobacteria From 2014-2021

In Korea, the incidence of Mycobacterium tuberculosis infections has decreased; however, the incidence of lung diseases attributed to Non-Tuberculous Mycobacteria (NTM) is increasing. This study aimed to elucidate the isolation rate and distribution of NTM recently isolated at a Korean test center. Respiratory samples for acid-fast bacilli culture collected between January 2014 and December 2021 at a test center in Yongin-si were targeted. Acid-fast bacilli solid and liquid media culture and NTM identification tests were conducted. In NTM cultures, the positivity rate was increased in solid (3.7%) and liquid (5.3%) media in 2021, compared to that observed in 2014. NTM identification tests increased from 922 in 2014 to 3,385 in 2018 and 4,058 in 2021. The average NTM infection age increased from 64.7 years in 2014 to 68.5 years in 2021. NTM infections among those aged ≥61 years were substantially increased. The most frequently detected NTM species was Mycobacterium intracellulare (40.9%), followed by Mycobacterium avium (23.1%), with Mycobacterium avium complex considered dominant. The results suggest that NTM management in older individuals is necessary. We also confirmed the age and species-specific isolation rates and distribution of NTM, which can be helpful for NTM identification and NTM drug susceptibility testing. Moreover, it will be able to guide antibacterial agent selection and treatment.