The purpose of this study is to investigate if the probiotic Bifidobacterium breve Bif195 (Bif195) will result in improvement in clinical outcome in patients with diarrhea-predominant irritable bowel syndrome (IBS).

IBS is the most frequently diagnosed gastrointestinal disease and also the most common cause of referrals to gastroenterology departments in Denmark.

The possibilities for treatment for IBS are limited. Treatment strategies that involve the microbiota provide symptom relief in some IBS patients. Several studies have demonstrated that the composition of the gut microbiota in IBS patients is different from healthy controls.

Probiotic interventions has shown promising results, but it currently remains unknown which probiotics are effective and which are not.

A new probiotic bacterium, Bifidobacterium breve Bif195 (Bif195) has been identified and has shown great effects on preventing enteropathy and ulcers on the gut mucosa in healthy volunteers given acetylsalicylic acid, and thereby Bif195 has also shown a potential in reducing gut permeability defects. This bacterium has not yet been investigated in IBS patients.

Inclusion Criteria:

• Diagnosed with IBS-D defined as more than one-fourth (25%) of bowel movements with Bristol Stool Scale Types 6-7 and less than one-fourth (25%) with Types 1-2
• Fulfill Rome IV diagnostic criteria for IBS
• Moderate to severe disease activity (IBS-SSS ≥175)
• Able to read and speak Danish
• Normal colonoscopy (performed within 1 year) if the patient had blood in stool

Exclusion Criteria:

• Other chronic gastro intestinal diseases including lactose intolerance and coeliac disease
• Fecal calprotectin ≥50 mg/kg
• Fecal sample positive for enteropathogenic microorganisms
• Surgical interventions in the GI region (except for appendectomy, hernia repair, cholecystectomy and gynecological and urological procedures)
• Psychiatric disorder
• Abuse of alcohol or drugs
• Medications except birth control pills, hormone supplements, allergies/asthma agents, blood pressure and cholesterol-lowering agents, proton pump inhibitors and non-prescription medicines; abnormal colonoscopy findings
• Pregnancy, planned pregnancy or breastfeeding females
• Ingestion of probiotics or antibiotics <4 weeks before the inclusion
• Abnormal screening biochemistry