Polyethylene Glycol and Intestinal Inflammation in Cystic Fibrosis

Inclusion Criteria: * Age ≥ 4 years old and \<18 years old ; * Patient with cystic fibrosis (sweat test \> 60 mmol/l and/or molecular biology identifying mutations in the CFTR gene) with associated pancreatic insufficiency (fecal elastase \<100 µg/g); * With a rapid calprotectin assay result via the IBDoc test (Bühlmann®) superior or equal to 250 µg/g; * Person affiliated or benefiting from a social security scheme; * Free, informed and written consent signed by the holders of parental authority and the investigator before any examination required by the research and oral and/or written consent by the participant (depending on his/her age). Exclusion Criteria: * Ongoing processing that can modulate the functionality of the CFTR (such as lumacaftor-ivacaftor protein therapy); * Patient already on polyethylene glycol or other laxative within 3 months before the inclusion visit; * Patient with diarrhea at inclusion (diarrhea will be defined as the presence of 3 or more stools / day in the 7 days prior to the inclusion visit); * Acute viral or bacterial diarrhea in the month prior to the inclusion visit (associated with fever); * Cure of oral or intravenous antibiotics or antifungals in the month preceding the collection of samples; * Change in background treatment in the month prior to the inclusion visit (oral or inhaled corticosteroid therapy, azithromycin, inhaled antibiotic therapy, inhaled antifungal agent, proton pump inhibitors); * Taking probiotics in the month before…