Comparing the harmful effects of nontuberculous mycobacteria and Gram negative bacteria on lung function in patients with cystic fibrosis

Background: To better understand the relative effects of infection with nontuberculous mycobacteria and Gram negative bacteria on lung function decline in cystic fibrosis, we assessed the impact of each infection in a Danish setting. Methods: Longitudinal registry study of 432 patients with cystic fibrosis contributing 53,771 lung function measures between 1974 and 2014. We used a mixed effects model with longitudinally structured correlation, while adjusting for clinically important covariates. Results: Infections with a significant impact on rate of decline in %FEV1 were Mycobacterium abscessus complex with -2.22% points per year (95% CI -3.21 to -1.23), Burkholderia cepacia complex -1.95% (95% CI -2.51 to -1.39), Achromobacter xylosoxidans -1.55% (95% CI -2.21 to -0.90), and Pseudomonas aeruginosa -0.95% (95% CI -1.24 to -0.66). Clearing M. abscessus complex was associated with a change to a slower decline, similar in magnitude to the pre-infection slope. Conclusions: In a national population we have demonstrated the impact on lung function of each chronic CF pathogen. M. abscessus complex was associated with the worst impact on lung function. Eradication of M. abscessus complex may significantly improve lung function.