Introduction: Pseudomonas aeruginosa infection is associated with higher mortality and worse quality of life in bronchiectasis. Identification of risk factors for new isolation of P. aeruginosa could guide the use of eradication treatment.

Methods: The EMBARC European Bronchiectasis Registry is a prospective observational study across 30 countries. Patients with history of P. aeruginosa infection at baseline were excluded. Subsequent identification of P. aeruginosa in sputum on at least one occasion in the next 3 years was regarded as new P. aeruginosa isolation. Risk factors were identified by logistic regression.

Results: 10443 patients without P. aeruginosa at baseline were studied. 428 new P. aeruginosa infections were recorded during follow-up (4.1%). Independent risk factors for new isolation of P. aeruginosa were worse lung function (p=0.003), frequent exacerbations (OR 1.05 95% CI 1.01-1.09,p=0.01), worse radiological severity (OR 1.08 95% CI 1.04-1.11,p<0.00001), current inhaled corticosteroid treatment OR 1.32 95% CI 1.04-1.66,p=0.02, macrolide therapy OR 1.40 95% CI 1.08-1.80,p=0.01, lower BMI 0.97 95% CI 0.95-0.99,p=0.002 and higher daily sputum production OR 1.03 95% CI 1.01-1.05,p=0.007. Risk was equal across all aetiologies except for primary ciliary dyskinesia where risk of P. aeruginosa isolation was increased OR 2.84 95% CI 1.41-5.73,p=0.003. Patients managed in non-specialist centres had a higher risk of new P. aeruginosa isolation 1.32 95% CI 1.04-1.66,p=0.02).

Conclusion: Risk factors for new isolation of P. aeruginosa are linked to disease severity, underlying primarily ciliary dyskinesia and may be linked to quality of care.