Clinical and prognostic characteristics of stable bronchiectasis in adults with pseudomonas aeruginosa colonization: a prospective cohort study

Background: Bacterial infection and colonization are gradually associated with disease severity and prognosis in bronchiectasis. The impact of Pseudomonas aeruginosa (PA) colonization on the clinical features and disease progression in stable bronchiectasis remains unclear. This study aims to investigate the association between PA colonization and lung function as well as prognosis in stable bronchiectasis. Methods： This prospective cohort study enrolled patients with stable bronchiectasis, with or without PA colonization, in Shanghai between January 2020 and December 2023. We compared the baseline data including clinical characteristics, laboratory findings, and lung function. During follow-up until December 2024, we monitored lung function at the first follow-up visit and recorded the time to first exacerbation. Results： A total of 391 patients with stable bronchiectasis were enrolled, including 118 (30.2%) with PA colonization. These patients showed significantly higher age, BMI <18.5 kg/m ² , disease duration, affected lobes, modified Reiff score, BSI, E-FACED score, exacerbations and related hospitalizations in the prior year, chronic PA colonization, purulent sputum, cough, wheezes, crackles, CRP, and CD4⁺T cell counts<500. Conversely, BMI, other bacterial colonization, and CD4⁺T cell was lower in PA colonization group. Among 210 patients who completed at least one lung function follow-up, forced vital capacity (FVC), FVC%predicted, forced expiratory volume in 1 second (FEV ₁ ), FEV ₁ %predicted, and FEV₁/FVC ratio at the first follow-up were significantly lower than baseline. After propensity score matching, 87 patients (32 PA colonization, 55 non-PA colonization) were included. The PA colonization group showed significantly greater declines in DFEV ₁ and DFEV ₁ /FVC ratio. Survival analysis revealed a significantly shorter median time to first exacerbation in patients with PA colonization than in those without (202 days vs 328 days). PA colonization was associated with exacerbation of bronchiectasis (HR=1.571; 95%CI: 1.014-2.432). Conclusion： PA colonization in stable bronchiectasis was associated with a more severe disease profile, along with accelerated lung function decline and increased exacerbation risk. These results suggested that PA colonization contribute to the progression of bronchiectasis.