Nontuberculous mycobacteria (NTM) are emerging as notable causative agents of opportunistic infections. To examine clinical significance, species distribution, and temporal trends of NTM in Denmark, we performed a nationwide register-based study of all unique persons with NTM isolated in the country during 1991–2022. We categorized patients as having definite disease, possible disease, or isolation by using a previously validated method. The incidence of pulmonary NTM increased throughout the study period, in contrast to earlier findings. Mycobacterium malmoense, M. kansasii, M. szulgai, and M. avium complex were the most clinically significant species based on microbiologic findings; M. avium dominated in incidence. This study shows the need for surveillance for an emerging infection that is not notifiable in most countries, provides evidence to support clinical decision-making, and highlights the importance of not considering NTM as a single entity.

非结核分枝杆菌（NTM）正在成为机会性感染的显着病原体。为了检查丹麦 NTM 的临床意义、物种分布和时间趋势，我们对 1991 年至 2022 年期间在该国隔离的所有 NTM 独特个体进行了一项全国范围的登记研究。我们使用先前验证的方法将患者分为患有明确疾病、可能疾病或隔离的患者。与早期的研究结果相反，在整个研究期间，肺部 NTM 的发生率有所增加。根据微生物学发现，马尔默分枝杆菌、堪萨斯分枝杆菌、苏尔盖分枝杆菌和鸟分枝杆菌复合体是临床上最重要的菌种；鸟分枝杆菌在发病率中占主导地位。这项研究表明需要对大多数国家不需通报的新发感染进行监测，提供支持临床决策的证据，并强调不将 NTM 作为单一实体的重要性。