Seven decades of nontuberculous mycobacteria in Denmark: shifts in species distribution and clinical relevance

Iversen, XES, Norman, A, Folkvardsen, DB, Rasmussen, EM, Svensson, E, Rigouts, L, Meehan, C ORCID: https://orcid.org/0000-0003-0724-8343, Jelsbak, L and Lillebaek, T, 2026. Seven decades of nontuberculous mycobacteria in Denmark: shifts in species distribution and clinical relevance. Journal of Clinical Microbiology. ISSN 0095-1137

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Abstract

The global burden of human disease caused by nontuberculous mycobacteria (NTM) is steadily increasing. Using our unique historical collection of freeze-dried mycobacterial isolates at the Statens Serum Institut, Copenhagen, we investigated long-term trends in NTM clinical relevance and species distribution in Denmark over the past seven decades. A total of 666 historical NTM isolates from human samples collected between 1948 and 1978 were compared with 1,820 contemporary isolates identified during routine diagnostics from 2013 to 2022. Species identification was performed for all isolates using the GenoType CM and AS line-probe assays. Among historical isolates, 16 different species were identified, with the majority classified as Mycobacterium sp. (32.1%, n = 214). In contrast, recent isolates were dominated by Mycobacterium avium (39.6%, n = 721), while Mycobacterium sp. accounted for only 7.8% (n = 142). Furthermore, notable changes in prevalence over time at the single species level were observed for M. avium and Mycobacterium abscessus. Further genomic analyses of historical Mycobacterium sp. isolates revealed several uncommon or previously unrecognized species rarely detected in current diagnostic settings. In conclusion, our findings suggest a significant shift in the spectrum of species responsible for human NTM infections in Denmark over the past seven decades, with possible implications for diagnostic strategies, clinical management, and public health surveillance.

Item Type:	Journal article
Publication Title:	Journal of Clinical Microbiology
Creators:	Iversen, X.E.S., Norman, A., Folkvardsen, D.B., Rasmussen, E.M., Svensson, E., Rigouts, L., Meehan, C., Jelsbak, L. and Lillebaek, T.
Publisher:	American Society for Microbiology
Date:	20 April 2026
ISSN:	0095-1137
Identifiers:	Number Type 10.1128/jcm.01561-25 DOI 2680439 Other
Rights:	Copyright © 2026 Iversen et al. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/).
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Borcherds
Date Added:	28 Apr 2026 10:32
Last Modified:	28 Apr 2026 10:32
URI:	https://irep.ntu.ac.uk/id/eprint/55615

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