Risk factors for new P. aeruginosa isolation in bronchiectasis- data from the European Bronchiectasis Registry (EMBARC)

<b>Introduction:</b><i>Pseudomonas aeruginosa</i> infection is associated with higher mortality and worse quality of life in bronchiectasis. Identification of risk factors for new isolation of <i>P. aeruginosa</i> could guide the use of eradication treatment. <b>Methods:</b> The EMBARC European Bronchiectasis Registry is a prospective observational study across 30 countries. Patients with history of <i>P. aeruginosa</i> infection at baseline were excluded. Subsequent identification of <i>P. aeruginosa</i> in sputum on at least one occasion in the next 3 years was regarded as new <i>P. aeruginosa</i> isolation. Risk factors were identified by logistic regression. <b>Results:</b> 10443 patients without <i>P. aeruginosa</i> at baseline were studied. 428 new <i>P. aeruginosa</i> infections were recorded during follow-up (4.1%). Independent risk factors for new isolation of <i>P. aeruginosa</i> 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&lt;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 <i>P. aeruginosa</i> isolation 1.32 95% CI 1.04-1.66,p=0.02). <b>Conclusion:</b> Risk factors for new isolation of <i>P. aeruginosa</i> are linked to disease severity, underlying primarily ciliary dyskinesia and may be linked to quality of care.