• Microbiota have a natural effect upon fermentation, motricity and digestive sensitivity and upon certain constituents of the brain-gut axis.
• In 15% of cases, IBS arises following an "ecological" disruption, such as the taking of antibiotics or an intestinal infection.
• In persons with IBS, microbial proliferation is sometimes observed in the small intestines.
• Qualitative and quantitative abnormalities in the fecal and mucosal microbiota are observed.
• Studies carried out on animals have shown that manipulation of microbiota par antibiotics, probiotics, transfer of microbiota, etc. has an effect upon IBS.
• Therapeutic control trials in humans showed the efficacy of certain probiotics and antibiotics upon this condition.

Much research aimed at improving our knowledge of IBS and finding new treatments is now in progress.