Effect of Fecal Microbiota Transplantation in Irritable Bowel Syndrome

Inclusion Criteria: * Fulfilled Rome III diagnostic criteria for IBS * Moderate-severe disease activity (IBS-Symptom Severity Score ≥175) * Able to read and speak Danish * Normal colonoscopy at age ≥ 40 years (performed within 1 year) or blood in stool Exclusion Criteria: * Other chronic gastrointestinal disease * Positive fecal sample with enteropathogenic microorganisms or Clostridium difficile * Positive screening for HIV, Hepatitis B or HCV antibody * Surgical interventions in the gastrointestinal region (except for appendectomy, hernia repair, cholecystectomy, and gynecological and urological procedures) * Psychiatric disorder * Fecal calprotectin ≥ 50 mg/kg * Abuse of alcohol or drugs * Medications other than birth control pills, hormone supplements, allergies and asthma agents, blood pressure and cholesterol lowering agents, proton pump inhibitors and non-prescription medicines * Abnormal screening biochemistry * Abnormal colonoscopy findings * Pregnant, planned pregnancy or breastfeeding females * Ingestion of probiotics or antibiotics \< 8 weeks before the inclusion Inclusion criteria for donors * Age between 18-45 years * Past and current healthy * Normal weight (BMI between 18,5-24,9 kg/m2) * Normal bowel movements (defined as 1-2 per day and type 3-4 at Bristol Stool Form Scale) * No medication consumption Exclusion criteria for donors * Known or high risk of infectious diseases such as HIV, hepatitis A, B or C * Positive stool sample for C. difficile toxin, parasites or other pathogens * Antibiotic treatment in the past 6 months * Abuse of alcohol or drugs * Smoking * Tattoo or body piercing within the last 6 months * Allergy, asthma or eczema * Family history of gastrointestinal diseases * Participation in high-risk sexual behaviors * Born by Caesarean section