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Irritable bowel syndrome

Recurring belly pain with changes in bowel habits, without visible damage to the gut.

Compared within 2 studies that had both: 372 people with irritable bowel syndrome and 185 healthy people. 38 microbes are less common in people with irritable bowel syndrome, and 13 more common.

A difference is an association: it doesn’t mean these microbes cause, prevent or treat irritable bowel syndrome.

Phylum

Searching opens both lists and shows only matching rows.

Less common in irritable bowel syndrome · 38

Strongest first, then the biggest gap · Each figure is 10 people Strongest first · Each figure is 10 people
  1. Faecalicatena fissicatena in 2 studies Healthy 49% irritable bowel syndrome 20%
  2. Oscillibacter sp. ER4 in 2 studies Healthy 47% irritable bowel syndrome 19%
  3. Faecalibacterium butyricigenerans in 2 studies Healthy 38% irritable bowel syndrome 14%
  4. Wujia chipingensis in 2 studies Healthy 28% irritable bowel syndrome 8.9%
  5. Bifidobacterium adolescentis in 2 studies Healthy 52% irritable bowel syndrome 29%

More common in irritable bowel syndrome · 13

Strongest first, then the biggest gap · Each figure is 10 people Strongest first · Each figure is 10 people
  1. Blautia caecimuris in 2 studies Healthy 16% irritable bowel syndrome 39%
  2. Streptococcus salivarius in 2 studies Healthy 22% irritable bowel syndrome 45%
  3. Lachnospiraceae bacterium EP-SM-12S-S03 in 2 studies Healthy 0% irritable bowel syndrome 5.1%
  4. Escherichia coli in 2 studies Healthy 4.5% irritable bowel syndrome 18%
  5. Bacillota bacterium in 2 studies Healthy 6.6% irritable bowel syndrome 20%

Where these numbers come from

Studies
Only GMrepo projects that had people with the condition and healthy people, 10 or more of each. Numbers come from those studies, never from pooling.Sampled in the United States.
How common
The share of people whose sample has any of it, in the people with the condition and in the healthy people of those same studies. Tested within studies (Cochran–Mantel–Haenszel, corrected for testing many microbes); a difference counts when it is clear and meaningful (Cohen’s h of 0.2 or more).
Strength word
Counted by code from how many studies point the same way: Seen again and again (3 or more, none clearly the other way), Seen more than once (2, the majority), Seen once (1, listed last). Where studies disagree, a row isn’t listed.
Each study
Tap a row for every study’s own numbers, and for how much carriers have.
Analysis
Our analysis of GMrepo data. GMrepo on Data sources · Read the rules

Also compared · 228 microbes

Compared within studies that had both, but not listed above.

Studies disagree · 13

No meaningful difference · 215
PubMed · human studies and reviews first

Recent research

All research on it
  1. Randomized trial Journal of gastroenterology and hepatology · 2026
    Consolidation Therapy of Probiotics With Rifaximin Prevent Relapse in Rifaximin-Responsive Diarrhea-Predominant Irritable Bowel Syndrome: A Multicenter Randomized Clinical Trial.
    PubMed ↗
  2. Review Reviews on environmental health · 2026
    Dietary patterns, gut microbiota, and gastrointestinal disorders: mechanistic insights into irritable bowel syndrome and inflammatory bowel disease.
    PubMed ↗
  3. Observational Journal of pediatric gastroenterology and nutrition · 2026
    Gut microbiome in pediatric acute pancreatitis and Crohn's disease versus irritable bowel syndrome and healthy controls.
    PubMed ↗
  4. Randomized trial Journal of gastroenterology and hepatology · 2025
    Probiotic Blend of Lactobacillus acidophilus LA-5 and Bifidobacterium animalis ssp. Lactis BB-12 in Non-constipated Irritable Bowel Syndrome: A Double-Blind Randomized Placebo-Controlled Trial.
    PubMed ↗
  5. Review British journal of hospital medicine · 2025
    The Role of Colonic Microbiota in Constipation Predominant Irritable Bowel Syndrome: A Literature Review.
    PubMed ↗

Source: PubMed, U.S. National Library of Medicine · 144 linked papers, last 10 years