[Microbiota and irritable bowel syndrome: A critical inventory]

This narrative review critically explores the role of the gut microbiota in functional bowel disorders of IBS-type. Starting with changes in the microbiota composition and diversity, as they have been often found in correlative IBS studies, it raises the question of cause and consequence, of sensitivity and specificity of findings in comparison to other diseases, and of the scientific and clinical options to manipulate the microbiota. This includes a discussion of pre- and probiotics and antibiotics as well as the role of nutrition and the microbiota exchange with fecal microbiota transfer (FMT). For IBS, most of these strategies have not been found to be successful therapies. This may be due to the heterogeneity of the disease itself, but eventually also due to the concepts of microbiological research, e. g., the term dysbiosis, or in methodological differences of the molecular-genetic research that are not visible in the published papers. Future studies should aim to identify those factors that may explain and predict the response to such therapies.