Distinct microbial populations exist in the mucosa-associated microbiota of sub-groups of irritable bowel syndrome

Neurogastroenterol Motil. 2012 Jan;24(1):31-9. doi: 10.1111/j.1365-2982.2011.01803.x. Epub 2011 Nov 9.


Background: There is increasing evidence to support a role for the gastrointestinal microbiota in the etiology of irritable bowel syndrome (IBS). Given the evidence of an inflammatory component to IBS, the mucosa-associated microbiota potentially play a key role in its pathogenesis. The objectives were to compare the mucosa-associated microbiota between patients with diarrhea predominant IBS (IBS-D), constipation predominant IBS (IBS-C) and controls using fluorescent in situ hybridization and to correlate specific bacteria groups with individual IBS symptoms.

Methods: Forty-seven patients with IBS (27 IBS-D and 20 IBS-C) and 26 healthy controls were recruited to the study. Snap-frozen rectal biopsies were taken at colonoscopy and bacterial quantification performed by hybridizing frozen sections with bacterial-group specific oligonucleotide probes.

Key results: Patients with IBS had significantly greater numbers of total mucosa-associated bacteria per mm of rectal epithelium than controls [median 218 (IQR - 209) vs 128 (121) P = 0.007], and this was chiefly comprised of bacteroides IBS [69 (67) vs 14 (41) P = 0.001] and Eubacterium rectale-Clostridium coccoides [52 (58) vs 25 (35) P = 0.03]. Analysis of IBS sub-groups demonstrated that bifidobacteria were lower in the IBS-D group than in the IBS-C group and controls [24 (32) vs 54 (88) vs 32 (35) P = 0.011]. Finally, amongst patients with IBS, the maximum number of stools per day negatively correlated with the number of mucosa-associated bifidobacteria (P < 0.001) and lactobacilli (P = 0.002).

Conclusions & inferences: The mucosa-associated microbiota in patients with IBS is significantly different from healthy controls with increases in bacteroides and clostridia and a reduction in bifidobacteria in patients with IBS-D.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bacteria / genetics
  • Biopsy
  • Female
  • Humans
  • Intestinal Mucosa / microbiology*
  • Intestinal Mucosa / pathology
  • Irritable Bowel Syndrome / microbiology*
  • Irritable Bowel Syndrome / pathology
  • Irritable Bowel Syndrome / physiopathology
  • Male
  • Metagenome*
  • Rectum / anatomy & histology
  • Rectum / microbiology
  • Rectum / surgery