This study aims to investigate the characteristics of gut microbiome and metabolome in non-CF bronchiectasis patients, hoping to explore the underlying mechanisms as well as the influence of gut microbiota composition on bronchiectasis.

Non-cystic fibrosis bronchiectasis is a chronic airway disease characterized by irreversible and progressive dilation of the large airways, bronchi and bronchioles, which severely impairs the life quality of patients and increases the social and economic burden. It is also a heterogenous disease affected by multiple factors such as geography and ethnicity. The incidence of bronchiectasis among the Chinese population is about 1.2%, which has clearly been underestimated. However, due to the lack of awareness, the research of bronchiectasis in China is still in its infancy. Colonization and recurrent infection of pathogen is the primary unsolved problem in clinical practice. With the proposition of "gut-lung axis" theory, the role of gut microbiota in the pathogenesis of respiratory diseases has been gradually revealed. Evidences have shown that gut microbiota regulates respiratory immunity via releasing soluble bacterial components and its metabolites into the circulation, as well as facilitating the migration of immune cells directly to the lung. In the 1980s, a patient after a colectomy has been reported to generate bronchiectasis. The most common clinical manifestation of pulmonary involved IBD patients is also bronchiectasis, suggesting that the "gut-lung axis" may be involved in the pathogenesis of bronchiectasis. Therefore, clarifying the role and mechanism of gut microbiota in bronchiectasis and its gut microbiome is expected to provide new theoretical basis and ideas for its diagnosis and treatment.

Inclusion Criteria:

• Written informed consent
• Regular bowel movement: every 2 days - 3 times/ day
• The diagnose of bronchiectasis should refer to "BTS guideline 2010"

Exclusion Criteria:

• Diagnosis of ABPA
• Pregnancy or lactation
• Active smoking or alcohol using within last 6 months
• HIV infection
• Previous abdominal or rectal surgery
• Diagnosis of chronic gastrointestinal disease, heart disease, diabetes, severe renal insufficiency (GFR < 30ml/min) or immunodeficiency
• Regular use of the following types of medications (> 2 times per week) within last 2 months: opium, loperamide antidiarrheal, systemic antihistaminic, metoclopramide, proton pump inhibitor
• Poor compliance or inability to cooperate as judged by the doctor

Patients enrolled in this study should meet the diagnositc criteria of BTS guideline 2010" . Patients with a history of antibiotic use were admitted to the study. Healthy volunteers were eligible for inclusion provided they had not received antibiotics within the previous one month.