Objectives: To determine the bacterial and viral spectrum at steady-state and exacerbation of COPD-Bronchiectasis association (CBA), and the association between pathogen detection and exacerbations.

Methods: We prospectively collected sputum from patients with CBA, and bronchiectasis with (BO) and without airflow obstruction (BNO) for bacterial culture and viral detection.

Results: We enrolled 76 patients with CBA, 58 with BO, and 138 with BNO. Bacterial detection rate increased from BNO, CBA to BO at steady-state (P=0.02), but not at exacerbation (P=0.91); while no significant differences in viral detection rate were found. Compared with steady-states, viral isolations (V+) occurred more frequently during exacerbation in BNO (P=0.001) and CBA (P=0.036), but not in BO (P=0.904); as did isolation of bacterial plus viral isolation (V+B+). In CBA, isolation of any viruses (OR:1.63, 95%CI[1.11-2.39]), Human metapneumovirus (OR:3.55, 1.07-12.52) and bacterial plus viruses (OR:1.68, 1.04-2.71) was associated with exacerbation. Repeated detection of Pseudomonas aeruginosawas (PA) associated with shorter time to the first exacerbation in CBA (HR=2.07, 1.19-3.61) but not in patients with BO.

Conclusions: Isolation of any viruses, Human metapneumovirus and bacterial plus viruses was associated with CBA exacerbations. Repeated PA isolation imposed different impact of future exacerbation on patients with CBA from those with BO.