Exploring gut microbes in adults with IBS and constipation who produce excess methane

Single-center Exploratory Study of the Intestinal Microbiota in Patients Suffering of Irritable Bowel Syndrome With Predominant Constipation and Methane Production: METHANOBIOTE

This study tests whether stool and blood samples show distinct gut microbes in adults with IBS and predominant constipation who have high methane on a breath test.

Quick facts

• Study type: Observational
• Enrollment: 40 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Hospices Civils de Lyon (Academic / other)
• Locations: 1 site (Lyon)
• Trial ID: NCT06801184 on ClinicalTrials.gov

What this trial studies

This single-center, observational study enrolls adults with IBS (Rome IV) who have predominant constipation, mixed bowel habits, or unspecified type and who show high methane (≥10 ppm) on a glucose breath test. Investigators collect stool and plasma samples to characterize the intestinal microbiota and its relationship to methane production and constipation symptoms. Participants who used antibiotics or probiotics in the past three months are excluded to avoid confounding the microbiota profile. The work aims to map microbial patterns, particularly methanogenic archaea like Methanobrevibacter smithii, in people with methane-associated constipation.

Who should consider this trial

Good fit: Adults (≥18) with IBS by Rome IV criteria who have predominant constipation (or mixed/unspecified types) and a high methane level (≥10 ppm) on a glucose breath test, and who have not taken antibiotics or probiotics in the past three months.

Not a fit: People without elevated methane on breath testing, those recently treated with antibiotics or probiotics, and patients whose IBS is diarrhea‑predominant are unlikely to be eligible or to benefit from this study's findings.

Why it matters

Potential benefit: If successful, the findings could point to microbial targets or biomarkers that help guide more personalized treatments for constipation-predominant IBS.

How similar studies have performed: Prior studies have documented higher Methanobrevibacter smithii in constipation‑predominant IBS and have used breath tests to detect methane, but microbiota‑directed interventions remain largely exploratory.

Eligibility criteria

Inclusion Criteria:

* Patient suffering from Irritable Bowel Syndrome (IBS) (abdominal pain for the past 6 months occurring on average at least 1 day per week in the last 3 months, with at least 2 of the following criteria: associated with defecation, associated with a change in stool frequency, associated with a change in stool consistency):

  1. Predominant constipation type (IBS-C): Bristol Stool Scale 1-2 ≥ 25% of the time and Bristol Stool Scale 6-7 ≤ 25% of the time
  2. Alternating diarrhea-constipation type (IBS-M): Bristol Stool Scale 1-2 25% of the time and Bristol Stool Scale 6-7 25% of the time
  3. Unspecified type: absence of sufficient criteria to meet criteria for IBS-C, IBS-D, or IBS-M.
* Patient exhibiting a high methane level (≥ 10 ppm) during a glucose breath test.
* Aged ≥ 18 years at the time of study entry.
* Patient not opposing participation in the study.

Exclusion Criteria:

* Patient who has been treated with antibiotics or probiotics in the last 3 months prior to inclusion.
* Patient suffering from diarrhea-predominant IBS (Bristol Stool Scale 6-7 ≥ 25% of the time and Bristol Stool Scale 1-2 ≤ 25% of the time).
* Patient with a history of abdominal surgery other than appendectomy and cholecystectomy.
* Patient with a history of celiac disease.
* Patient with proven inflammatory bowel disease.
* Patient with a history of colorectal cancer.
* Patient with uncontrolled hypothyroidism.
* Patient with uncontrolled diabetes.
* Pregnant or breastfeeding women.
* Patient deprived of liberty by a judicial or administrative decision.
* Adult patient under legal protection (guardianship, curators).
* Patient unable to discontinue proton pump inhibitor treatment during the study period

Where this trial is running

Lyon

• Hôpital Edouard Herriot — Lyon, France (Recruiting)

Study contacts

• Study coordinator: François MION, Pr

Conditions Irritable Bowel Syndrome; gastroenterology; microbiota; constipation; methano-production