Gut Microbiota in Patients With Irritable Bowel Syndrome—A Systematic Review

Abstract

IBS vs controls Bifidobacterium Faecalibacterium Lactobacillaceae Bacteroides Enterobacteriaceae See Covering the Cover synopsis on 1. BACKGROUND & AIMS: Irritable bowel syndrome (IBS) is common but difficult to treat. Altering the gut microbiota has been proposed as a strategy for treatment of IBS, but the association between the gut microbiome and IBS symptoms has not been well established. We performed a systematic review to explore evidence for this association. METHODS: We searched databases, including MEDLINE, EMBASE, Cochrane CDSR, and CENTRAL, through April 2, 2018 for case-control studies comparing the fecal or colon microbiomes of adult or pediatric patients with IBS with microbiomes of healthy individuals (controls). The primary outcome was differences in specific gut microbes between patients with IBS and controls. RESULTS: The search identified 2631 citations; 24 studies from 22 articles were included. Most studies evaluated adults presenting with various IBS subtypes. Family Enterobacteriaceae (phylum Proteobacteria), family Lactobacillaceae, and genus Bacteroides were increased in patients with IBS compared with controls, whereas uncultured Clostridiales I, genus Faecalibacterium (including Faecalibacterium prausnitzii), and genus Bifidobacterium were decreased in patients with IBS. The diversity of the microbiota was either decreased or not different in IBS patients compared with controls. More than 40% of included studies did not state whether cases and controls were comparable (did not describe sex and/or age characteristics). CONCLUSIONS: In a systematic review, we identified specific bacteria associated with microbiomes of patients with IBS vs controls. Studies are needed to determine whether these microbes are a product or cause of IBS.

No distinct microbiome signature of irritable bowel syndrome found in a Swedish random population

“…37 While rifaximin, a non-absorbable antibiotic, is efficacious in a subset of IBS cases, it is unknown whether this is due to an antimicrobial or anti-inflammatory effect, or where the site of action may occur. 38 39 In a recent meta-analysis by Pittayanon and colleagues, 40 22 papers were included; two Chinese studies assessed colonic tissue while the rest only assessed stool microbiome. The reported data at the phylum level was conflicting.…”

A Clostridia-rich microbiota contributes to increased excretion of bile acids in diarrhea-predominant irritable bowel syndrome

“…In fact, the microbiota-based concept for subtyping IBS has been previously proposed by Jeffery, et al 45 Another study also has classified different enterotypes within the IBS category, linked with severity of symptoms, but authors pointed out the difficulty in stratifying IBS patients from healthy subjects when using only classic ecologic approaches 46 . Scrutinizing the linkage of microbial signature with the IBS subtype, varied results have been reported across studies 26 , a reduced microbial diversity and increased F/B ratio were more frequently found. 45 47 48 Our study did find an increased F/B ratio in this IBS-D cohort, but with no difference in the microbial richness.…”

“…Altered gut microbiota has been reported in the IBS-D population, 25 26 however, its link with excessive BA excretion has received little attention. Given the important role of gut microbiota in BA synthetic regulation and the appearance of gut dysbiosis, we hypothesized that gut dysbiosis may contribute to the excessive BA excretion in IBS-D. To investigate this hypothesis, BA-related metabolomic and metagenomic analyses were performed of an IBS-D cohort to identify the association of gut microbiota with BA disturbance.…”

Editorial: the overlap between dyspepsia and gastro‐oesophageal reflux—is duodenal eosinophilia the missing link?

“…7 The duodenum in turn is recognised to act as the master controller of gastroduodenal function and pathophysiological pertubations including the induction of pathological acid reflux into the oesophagus would not be unexpected in the setting of duodenal dysfunction but remains to be established. 4,8,9 We have postulated that duodenal eosinophilia may be an atopic disease that arises secondary to foods or in post-infectious functional dyspepsia and in the setting of duodenal microbiome dysbiosis. 9,10 We agree that the number of individuals in the functional dyspepsia subgroups was limited and the 95% confidence limits around the odds ratios were wide, although odds ratios over five suggest that confounding is unlikely and support a true pathophysiological association.…”

“…4,8,9 We have postulated that duodenal eosinophilia may be an atopic disease that arises secondary to foods or in post-infectious functional dyspepsia and in the setting of duodenal microbiome dysbiosis. 9,10 We agree that the number of individuals in the functional dyspepsia subgroups was limited and the 95% confidence limits around the odds ratios were wide, although odds ratios over five suggest that confounding is unlikely and support a true pathophysiological association. We agree that our findings need confirmation with a larger sample of subjects with all subtypes of functional dyspepsia and the underlying mechanisms of reflux symptoms documented by objective testing including oesophageal pH-impedance monitoring.…”