Abstract
Disease caused by nontuberculous mycobacteria (NTM) is reported to increase due to an ageing population and a rise in the proportion of immunosuppressed patients. We did a retrospective cohort study of NTM-disease in the Danish population through a quarter-century to determine the disease burden and trends in annual incidence rates. 524,119 clinical specimens were cultured for mycobacteria from 1991 through 2015 at the International Reference Laboratory of Mycobacteriology in Denmark. Among these, 8,227 NTM strains were identified from 3,462 patients and distributed according to microbiological disease criteria. We observed no increase in NTM disease incidence or proportion of patients with positive NTM cultures during the study period (Quasi-Poisson regression, p = 0.275 and 0.352 respectively). Annual incidence rates were 1.20/105 for definite NTM disease, 0.49/105 for possible NTM disease and 0.88/105 for NTM colonization. The incidence rate of NTM disease was highest in children aged 0-4 years (5.36/105/year), predominantly with cervical Mycobacterium avium complex (MAC) adenitis. Surprisingly, based on more than half a million clinical specimens cultured for mycobacteria in Denmark through 25 years, the NTM disease burden and trend in incidence in the Danish population has not increased opposed to numerous internationals reports.
Highlights
Disease caused by nontuberculous mycobacteria (NTM) is reported to increase due to an ageing population and a rise in the proportion of immunosuppressed patients
The increase in NTM disease has been attributed to different factors such as improved culturing techniques and greater disease awareness, but it has been attributed to a true increase in disease incidence as a result of increased life expectancy and an increasing proportion of the population experiencing immunosuppression due to medication or suffering from immune-modulating comorbidities such as e.g. diabetes mellitus and chronic obstructive pulmonary disease (COPD)[11,12,13]
Disease, 654 (19%) had possible NTM disease and 1,190 (34%) NTM colonization. 2,391 (69.1%) of samples were from pulmonary sites, 926 (26.7%) from non-pulmonary sites, and 145 (4.2%) from multifocal sites
Summary
Disease caused by nontuberculous mycobacteria (NTM) is reported to increase due to an ageing population and a rise in the proportion of immunosuppressed patients. We observed no increase in NTM disease incidence or proportion of patients with positive NTM cultures during the study period (Quasi-Poisson regression, p = 0.275 and 0.352 respectively). Based on more than half a million clinical specimens cultured for mycobacteria in Denmark through 25 years, the NTM disease burden and trend in incidence in the Danish population has not increased opposed to numerous internationals reports. NTM disease can mimic infection caused by Mycobacterium tuberculosis Both pulmonary NTM colonization and NTM disease have a five-year mortality of approximately 40%, reflecting the high level of comorbidity and/or immune suppression in these patients[4]. The majority of studies have been conducted in localized geographic regions within countries, sometimes based on few observations and/or short observation period, limiting the overall generalizability of results[5, 8, 10, 14, 15]
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