Subjects 15 adult patients (> 18 years) with CF, homozygote for the mutation ΔF508, are studied. They are all pancreas insufficient (fecal elastase < 100 µg/g), with no previous intestinal resection or lung transplantation. None of them have diabetes. Patients are all in well-regulated pancreatic enzyme replacement therapy (PERT), thriving and with stabile weight over the last half year. They have had no treatment with antibiotics in the last 14 days up to the examination.