Associations of Clinical Symptoms and Bowel Characteristics With Intestinal Microbiota in Patients With Irritable Bowel Syndrome: ACG Governors Award for Excellence in Clinical Research

Abstract

Introduction: The intestinal microbiota has been suggested as an important factor in the pathogenesis of IBS. However, most of the studies characterizing the intestinal microbiota in IBS focused on IBS diagnosis and its subtypes as defined by the Rome criteria. The associations between the intestinal microbiota, specific IBS symptoms and altered bowel habits have not been adequately investigated. Aim: To investigate the relationship between the intestinal microbiota, IBS-related GI symptoms and bowel characteristics. Methods: Fresh fecal samples were collected from IBS patients (Rome III criteria) and healthy controls (HC). Clinical variables included severity and frequency of abdominal pain, abdominal bloating and IBS symptom severity (IBS-SSS). Bowel characteristics were assessed by average daily stool frequency and consistency. The intestinal microbiota was investigated by phylogenetic microarray analysis. Analysis was done using linear models and correlation analyses were done using Spearman's (for ordinal data) and Pearson (for continuous data) coefficients both with Benjamini-Hochberg false discovery rate (FDR) correction for multiple comparisons. Random forest analysis (Breiman 2001) was carried out for selection of the bacteria most contributing to the outcome. Results: A total of 83 IBS patients and 24 HC were investigated. We found significant associations (p < 0.05) between specific bacterial taxa and several clinical variables. For example, several Bacteroides groups correlated positively with pain and negatively with IBS-QOL. In contrary Bifidobacteria correlated negatively with IBS severity and positively with IBS-QOL. Random forest analysis showed a set of 5 bacterial groups that explain 33% of variation in stool consistency (Clostridium leptum, Papillibacter cinnamivorans Faecalibacterium prausnitzii, Clostridium stercorarium and Akkermansia) and 3 bacterial groups that explain 23% of the variance in stool frequency (Clostridium ramosum, Prevotella melaninogenica, and Papillibacter cinnamivorans) (Figure 1).Figure 1Conclusion: Subjective reports of specific clinical symptoms and altered bowel characteristics are associated with significant alterations in the composition of the intestinal microbiota. However, our findings indicate that the microbial alterations associated with clinical symptoms and bowel characteristics are different, thus suggesting a complex multifactorial role of the intestinal microbiota in the clinical experience of IBS.