Irritable bowel syndrome (IBS) is a common chronic functional disorder of the gastrointestinal (GI) tract characterized by chronic abdominal pain and altered bowel habits without organic disease. The global prevalence of IBS in 2012 was estimated to be 11.2%. The overall incidence of IBS in Taiwan was 106.54 per 10000 population from 2012 to 2018, which is similar to the global prevalence. IBS is associated with substantial costs to patients, healthcare system and society in terms of increased health care expenditures, loss of work productivity and decrease in quality of life (QoL). There is no definite treatment for IBS, and current available treatments are mainly directed at symptom relief.

The cause of IBS is not yet known; however, multiple factors play an important role in the pathogenesis of IBS, such as disturbed gut microbiota (dysbiosis), altered enteroendocrine cells, previous infections, genetics and diet. Treatment guidelines recommend medications focused on IBS symptoms, diets low in fermentable types of oligosaccharides, and the use of probiotics. Probiotics are live microorganisms using in dietary as supplemental products. They have the beneficial effect on gut microenvironment, and may be an effective treatment for global symptoms and abdominal pain in IBS. Probiotics were defined as live microbial feed supplements that benefit the host by improving the intestinal microbial balance. The strains most frequently used as probiotics belong to the genera Bifidobacterium and Lactobacillus. Some probiotics have anti-inflammatory activity while others can modulate visceral hypersensitivity. However, inconsistent efficacy of probiotic administration was reported in the previous literature. Hod K, et al. conducted a double-blind, placebo-controlled study to assess the effect of a probiotic mixture on symptoms and inflammatory markers in women with diarrhea-predominant IBS, but they did not demonstrate superiority of probiotics over placebo. However, some meta-analysis revealed efficacy of probiotics for treatment of IBS. A meta-analysis published in 2020 concluded the RR of IBS symptoms improvement or response with probiotics treatment was 1.52, however, with high heterogeneity. The duration, dose and single or combination of probiotics vary and need to be further evaluated. A review of probiotics in IBS suggests that probiotic supplements have a delayed eﬀect in the improvement of IBS symptoms. Khodadoostan M, et al. conducted a trial to evaluate the effect of probiotic administration immediately and 1 month after colonoscopy in diarrhea-predominant IBS patients, which revealed the use of probiotics had the beneficial effect on IBS symptoms. Furthermore, it can be said that reductions in symptoms and pain in the two treatment groups were not significantly different, but after 6 months of treatment, the effect of probiotics in patients who immediately use it after colonoscopy was more visible and more stable. Niu HL, et al studied the efficacy and safety of probiotics in patients with irritable bowel syndrome based on 35 randomized controlled trials, which reveals supplementation with a multi-strain probiotic has greater potential to improve IBS symptoms than a single strain, and there is also a trend toward a beneficial effect of Bifidobacterium on global IBS symptoms and pain scores. Therefore, investigators propose a trial to evaluate the efficacy of the use of multi-strain probiotics including Bifidobacterium which is immediately used after colonoscopy for IBS treatment.

It is novel to conduct the study to compare the efficacy and safety of probiotics which are delivered directly via colonoscopy and oral administration. The amount of stool for FMT is 30 to 100 grams; thus, around 1012 to 1013 CFU bacteria will be transplanted in an FMT procedure. In this trial, the investigators will transplant 2x1011 CFU multi-strain probiotics into the colon via colonoscopic spray. Probiotics may be safer than FMT due to minimal risk of transmission of pathogenic organisms. It is also easier to prepare probiotics than feces from a superdonor. If it works, colonoscopic probiotics spray may replace FMT in clinical practice.