Nontuberculous mycobacteria in the Danish population, incidence rate and clinical importance during 24 years

Abstract

Background: Disease caused by Nontuberculous Mycobacteria (NTM) is reported to increase in incidence due to an ageing population and a rise in the proportion of immunosuppressed patients. We did an epidemiological study of the Danish population through a quarter of a century to determine the burden of NTM disease and investigate trends in annual incidence rates of culture positive cases. Methods: From 1991 to 2014, nationwide data on patients with a positive NTM culture (n=3,690) were retrieved from the International Reference Laboratory of Mycobacteriology in Denmark. We assigned positive cultures into disease categories according to microbiological disease criteria, and investigated incidence rates according to demographic variables; age, sex, NTM species and site of NTM localization. Results: Annual NTM incidence was 1.30/100,000 for definite NTM disease, 0.51/100,000 for possible disease and 1.05/100,000 for NTM colonization. We found no increase of NTM disease cases in the study period (p for trend p=0.291) and no increasing trend of NTM culture positivity (p for trend p=0.314). The incidence was high in children aged 0-4 years (5.87/100,000/year) where the main finding was extra-pulmonary Mycobacterium avium complex (MAC) infection. The median age of adult NTM patients increased in the study period from 52.4 years to 63.9 years (p Conclusion: We found no trend towards an increase in the annual incidence rate of NTM disease or a positive NTM culture during the last 24 years in Denmark.