Bronchiectasis is a chronic inflammatory respiratory disease defined as the irreversible dilatation of one or more bronchi and is associated with chronic and frequently purulent expectoration, multiple exacerbations and progressive dyspnea. Bronchiectasis has a large heterogeneity. Different patients with bronchiectasis may have different etiology, clinical manifestations, and imaging features. Previous studies showed that there are significant relationship between the airway microbiome and the severity of the disease. For example, patient with airway Pseudomonas aeruginosa colonization has heavier symptoms, heavier severity, poorer quality of life, more acute exacerbations, and worse prognosis. A large number of studies have reported that long-term treatment of low-dose macrolides such as azithromycin or clarithromycin has anti-inflammatory and immunomodulatory effects, which can improve the clinical symptoms and disease progression of various chronic airway diseases, such as diffuse panbronchiolitis, chronic obstructive pulmonary disease, bronchiectasis. Both the 2017 European Respiratory Society guidelines and the 2019 British Thoracic Society Guideline recommend macrolide drugs for the treatment of chronic Pseudomonas aeruginosa colonization bronchiectasis or frequent acute exacerbations bronchiectasis, but the specific mechanism is unknown.This study is based on omics methods (Microbiology and Metabolomics) to deeply explore the composition of airway and gut microbiota in patients with bronchiectasis, the factors affecting the colonization of Pseudomonas aeruginosa and the mechanism of macrolides in the treatment of bronchiectasis. This project is a multicenter clinical study involving patients with bronchiectasis from Wuhan Union Hospital, Guizhou Provincial People's Hospital, and Yichang Central People's Hospital. Patients with bronchiectasis were recruited according to the inclusion and exclusion criteria. Clinical data were collected from these patients (including demographic information, clinical characteristics, pulmonary function, and lung imaging), along with spontaneously expectorated sputum, feces, and peripheral blood, and the patients were followed for 24 months. The microbiome, metabolome, and cytokines in sputum and feces were assessed, as well as cytokines, inflammatory mediators, and metabolites in peripheral blood. Through the above methods,investigators further understand the mechanism affecting progression of bronchiectasis and some factors that lead to the colonization of Pseudomonas aeruginosa, as well as mechanisms of macrolides in the treatment of bronchiectasis.