The Efficacy of Single-strain Probiotics in Patients With Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common, yet still not fully understood, gastrointestinal disorders in adults. One suspected etiology involves intestinal dysbiosis, i.e. both quantitative and qualitative alterations in intestinal microbiota composition, which affects the gut-brain axis. Probiotics are live microorganisms, which-administered at the right dose-are beneficial for human health; their mechanism of action involves modifying the gut microbiota. Clinical study reports document that probiotic administration is beneficial for patients with IBS. The ultimate clinical effects depend primarily on probiotic strain selection. Our research team evaluated a multi-strain probiotic formulation and a multi-strain synbiotic (a combination of probiotic strains with short-chain prebiotic fructooligosaccharides) formulation as part of two randomized placebo-controlled clinical trials in patients with IBS with predominant diarrhea. The results indicated a beneficial effect of these formulations on the clinical course of IBS assessed with the international IBS symptom severity scale (IBS-SSS), with each of the study formulations exhibiting efficacy in different fields. The formulation composed of a mixture of Bifidobacterium and Lactobacillus strains reduced the levels of pain and improved the quality of life, whereas the synbiotic formulation effectively improved bloating and had a beneficial effect on the general condition of the intestines. A systematic review and meta-analysis published in 2020 showed that high doses of single-strain formulations, particularly those containing Bifidobacterium or Lactobacillus strains, may be more effective in IBS patients. Other reports demonstrated a high efficacy of the new-generation probiotic Bacillus coagulans in IBS. Therefore, the main objective of this research project is to assess the efficacy of single-strain probiotics containing Bifidobacterium lactis or Bacillus coagulans in patients with IBS.