Methodological issues in the study of intestinal microbiota in irritable bowel syndrome

Abstract

Irritable bowel syndrome (IBS) is an intestinal functional disorder with the highest prevalence in the industrialized world. The intestinal microbiota (IM) plays a role in the pathogenesis of IBS and is not merely a consequence of this disorder. Previous research efforts have not revealed unequivocal microbiological signatures of IBS, and the experimental results are contradictory. The experimental methodologies adopted to investigate the complex intestinal ecosystem drastically impact the quality and significance of the results. Therefore, to consider the methodological aspects of the research on IM in IBS, we reviewed 29 relevant original research articles identified through a PubMed search using three combinations of keywords: “irritable bowel syndrome + microflora”, “irritable bowel syndrome + microbiota” and “irritable bowel syndrome + microbiome”. For each study, we reviewed the quality and significance of the scientific evidence obtained with respect to the experimental method adopted. The data obtained from each study were compared with all considered publications to identify potential inconsistencies and explain contradictory results. The analytical revision of the studies referenced in the present review has contributed to the identification of microbial groups whose relative abundance significantly alters IBS, suggesting that these microbial groups could be IM signatures for this syndrome. The identification of microbial biomarkers in the IM can be advantageous for the development of new diagnostic tools and novel therapeutic strategies for the treatment of different subtypes of IBS.

Keywords: Intestinal dysfunction, Irritable bowel syndrome, Intestinal microbiota, Bifidobacteria, New generation DNA sequencing

Core tip: Irritable bowel syndrome (IBS) is the intestinal functional disorder with the highest prevalence in the industrialized world. The intestinal microbiota (IM) plays a role in its pathogenesis. Since the methodological aspects of the research on IM in IBS have never been considered in detail before, we carried out a revision of 29 original research articles. We reviewed the scientific microbiological message in light of the experimental method adopted. The analytical revision of the studies referenced in our review leaded to the identification of microbial groups whose relative abundance resulted significantly altered in IBS. Such microbial groups are potential IM signatures of IBS.