Study 1 is a cross-sectional investigation. Patients with clinically stable bronchiectasis (symptoms, including cough frequency, sputum volume and purulence, within normal daily variations) will undergo baseline assessment consisting of history taking, routine sputum culture, 16srRNA pyrosequencing, measurement of sputum inflammatory markers, oxidative stress biomarkers and MMPs, and spirometry. Microbiota taxa will be compared between bronchiectasis patients and healthy subjects.