Summary

This nationwide, registry-based study examines the clinical significance, species distribution, and trends of nontuberculous mycobacteria (NTM) in Denmark from 1991 to 2022. Integrating microbiological data from the International Reference Laboratory of Mycobacteriology, Copenhagen, with population data from Statistics Denmark, it provides a comprehensive long-term perspective on NTM epidemiology.

Spanning nearly three decades, it is among the most extensive studies on NTM trends, revealing a rise in pulmonary cases while extrapulmonary and disseminated cases have declined—contrasting earlier Danish findings and emphasising the need for ongoing surveillance. The study confirms that M. malmoense, M. kansasii, M. szulgai, and M. avium complex are among the most clinically relevant species.

These findings are essential for clinical practice and public health, highlighting NTM as a dynamic and diverse group of infections and reinforcing the need for continued monitoring. With an aging population and rising immunosuppressive therapy use, proactive surveillance and improved management strategies are needed.