Mortality and exacerbations in chronic obstructive pulmonary disease associated with Stenotrophomonas maltophilia. A regional cohort study of 22,689 outpatients.

Objectives: The clinical significance of Stenotrophomonas maltophilia in patients with COPD is poorly understood. We aimed to determine whether a lower respiratory tract culture positive for S. maltophilia in COPD patients was independently associated with increased risk of death and hospitalisation for acute exacerbation of COPD (AECOPD). Methods: An observational cohort study following outpatients with COPD in Eastern Denmark between 2010 and 2018, with a follow-up period of five years. Presence of S. maltophilia was treated as a time-varying exposure, where patients were considered exposed at the time of the first isolation of S. maltophilia from the lower respiratory tract. The hazard ratio (HR) of death and hospitalisation for AECOPD was assessed using Cox regression. Results: Of the total 22,689 patients 459 (2.0%) had a lower respiratory sample with S. maltophilia. A total of 7,649 deaths (S. maltophilia positive: 243 (52.9%) and S. maltophilia negative: 7,406 (34.4%)) and 24,912 hospitalisations for AECOPD (S. maltophilia positive: 1,100 in 459 patients and S. maltophilia negative: 23,821 in 22,230 patients) were registered. We found that a lower respiratory tract culture positive for S. maltophilia was associated with both increased mortality: HR 3.3 (95% CI 2.6-4.3), and hospitalisation for AECOPD: HR 3.4 (95% CI 2.8-4.1). Conclusion: A lower respiratory tract culture positive for S. maltophilia in COPD patients was associated with a substantially increased mortality and hospitalisation for AECOPD. Randomised controlled trials are proposed to determine whether S. maltophilia should be the target for antibiotic treatment.