In our study, CD subjects showed an increased abundance of Ruminococcus and decreased abundance of Parabacteroides and Dialister. Enriched Ruminococcus is associated with irritable bowel syndrome (IBS) [56], transient blooms of pro-inflammatory Ruminococcus have been associated with active flare-ups in IBD [57] and has been found to secrete a unique L-rhamnose oligosaccharide that induces tumor necrosis factor alpha (TNF-a), a major pro-inflammatory cytokine [58]. This evidence concerns the gene TNF and irritable bowel syndrome.