Proximity to blue spaces and risk of infection with Pseudomonas aeruginosa in cystic fibrosis: A case-control analysis

Abstract

Background: The acquisition of Pseudonzonas aeruginosa in cystic fibrosis (CF) is associated with lower survival, decreased lung function, worse radiological scores, increased exacerbations and reduced nutritional status. Open water is a known reservoir and a potential source of exposure to P. aeruginosa. Methods: Twenty eight adult CF patients who had no history of P. aeruginosa and had negative P. aeruginosa IgG antibody levels, were matched by age and sex with 28 CF patients with chronic P. aeruginosa colonization. Straight line and closest walking distance from patient's residence to the nearest "blue space", i.e. surface water as determined by Google Earth, were compared between the two groups, and odds ratios (OR) were estimated using conditional logistic regression. Results: Patients who were never infected with P. aeruginosa lived significantly further away from a natural water source than P. aeruginosa colonized patients, both when considering shortest walking distance (mean 487 m vs 308 m, p = 0.014) and beeline (mean 324 m vs 202 m, p = 0.021). Conditional logistic regression (correcting for FEV1%) revealed ORs for chronic P. aeruginosa colonization of 0.35 (95% CI 0.13-0.98; p = 0.045) and 0.12 (95% CI 0.02-0.81; p = 0.028) for each doubling in the beeline or walking distance, respectively, between residence and open water. Conclusion: We discovered that adult CF patients without P. aeruginosa infection live significantly further from blue space than CF patients with chronic P. aeruginosa colonization. Within the limitations of a case control study, this may indicate that natural open water represents a source of infection by P. aeruginosa in CF. Registration: The study was approved by the local ethical committee of the UZ Leuven, Belgium (ML-5028). (C) 2015 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.