Irritable Bowel and Bacterial Overgrowth Syndromes: a Bacterial Link Hypothesis of Functional Disease

Abstract

Aim. Assessment of the irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth syndrome (SIBO) interlinkage. Key points. SIBO may represent a "peripheral" mechanism of IBS, aside to nonspecific inflammation, increased epithelial permeability and local immune system activation. In various assays, the SIBO rate in IBS patients was 4–46% vs. 0–13% in an intact cohort. A limited diagnosability of SIBO obscures the SIBO–IBS causal interplay. Impaired motility in IBS may predispose to the SIBO development. Proinflammatory cytokines and mediators in SIBO, in turn, provoke visceral hypersensitivity and intense motility, the key IBS factors. Both conditions relate to qualitative and quantitative changes in microbiota, which warrants the application of probiotic Lactobacillus and Bifidobacterium strains. Conclusion. Further research into the SIBO–IBS interface is required for developing optimal probiotic-based therapies.