Abstract
BACKGROUND: Bacterial infection and colonization are gradually associated with disease severity and prognosis in bronchiectasis. The impact of chronic Pseudomonas aeruginosa (PA) infection on the clinical features and disease progression in stable bronchiectasis remains unclear. This study aims to investigate the association between chronic PA infection and lung function as well as prognosis in stable bronchiectasis. METHODS: This prospective cohort study enrolled patients with stable bronchiectasis, with or without chronic PA infection, 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 chronic PA infection. 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, resolved chronic PA infection, purulent sputum, cough, wheezes, crackles, CRP, and CD4⁺T cell counts < 500. Conversely, BMI, other bacterial colonization, and CD4⁺T cell was lower in chronic PA infection group. Among 210 patients who completed at least one lung function follow-up, forced vital capacity (FVC), FVC%predicted, forced expiratory volume in 1 s (FEV1), FEV1%predicted, and FEV₁/FVC ratio at the first follow-up were significantly lower than baseline. After propensity score matching, 87 patients (32 chronic PA infection, 55 without chronic PA infection) were included. The chronic PA infection group showed significantly greater declines in ΔFEV1 and ΔFEV1/FVC ratio. Survival analysis revealed a significantly shorter median time to first exacerbation in patients with chronic PA infection than in those without (202 days vs. 328 days). Chronic PA infection was associated with exacerbation of bronchiectasis (HR = 1.571; 95%CI: 1.014–2.432). CONCLUSION: Chronic PA infection in stable bronchiectasis was associated with high disease severity, accelerated lung function decline and increased exacerbation risk. These results suggested that chronic PA infection contributes to the progression of bronchiectasis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12890-026-04145-x.