Global and deep molecular analysis of microbiota signatures in fecal samples from patients with irritable bowel syndrome.

Background & Aims: Irritable bowel syndrome (IBS) has been associated with disruptions to the intestinal microbiota, but studies have had limited power, coverage, and depth of analysis. We aimed to define microbial populations that can be used discriminate the fecal microbiota of patients with IBS from that of healthy subjects and correlate these with IBS intestinal symptom scores.

Methods: The microbiota composition was assessed by global and deep molecular analysis of fecal samples from 62 patients with IBS patients and 46 healthy individuals (controls). We used a comprehensive and highly reproducible phylogenetic microarray in combination with quantitative polymerase chain reaction.

Results: The intestinal microbiota of IBS patients differed significantly (P = .0005) from that of controls. The microbiota of patients, compared with controls, had a 2-fold increased ratio of the Firmicutes to Bacteroidetes (P = .0002). This resulted from an approximately 1.5-fold increase in numbers of Dorea, Ruminococcus, and Clostridium spp (P < .005); a 2-fold decrease in the number of Bacteroidetes (P < .0001); a 1.5-fold decrease in numbers of Bifidobacterium and Faecalibacterium spp (P < .05); and, when present, a 4-fold lower average number of methanogens (3.50 × 10(7) vs 8.74 × 10(6) cells/g feces; P = .003). Correlation analysis of the microbial groups and IBS symptom scores indicated the involvement of several groups of Firmicutes and Proteobacteria in the pathogenesis of IBS.

Conclusions: Global and deep molecular analysis of fecal samples indicates that patients with IBS have a different composition of microbiota. This information might be used to develop better diagnostics and ultimately treatments for IBS.