Fecal microbiota profiling in patients with irritable bowel syndrome and small intestinal bacterial overgrowth.

Quick Summary

This study compared gut bacteria in the stool of 52 people—some with IBS and SIBO, some with IBS alone, and healthy controls—using breath testing and genetic analysis. Researchers found that IBS patients with SIBO had lower levels of Firmicutes bacteria, which correlated with worse abdominal pain and symptoms but less pain sensitivity during rectal testing. The differences in gut bacteria between IBS patients with and without SIBO were relatively mild.

What Was Studied

Researchers investigated whether IBS patients with SIBO have different gut bacteria profiles compared to IBS patients without SIBO and healthy controls. The study enrolled 52 participants: 18 healthy controls, plus IBS patients divided into those testing positive or negative for SIBO using a glucose hydrogen breath test.

How the Study Was Conducted

Participants completed questionnaires measuring IBS symptom severity, abdominal pain, and quality of life. SIBO was diagnosed using a standard glucose hydrogen breath test. Visceral sensitivity (how sensitive the gut is to pain) was measured using rectal balloon distension (inflating a small balloon in the rectum to test pain thresholds). Researchers collected fresh stool samples and used 16S rRNA gene sequencing to identify and compare bacterial populations across groups. Full methodology not publicly available — summary based on abstract only.

Key Findings

• IBS patients with SIBO had significantly lower levels of Firmicutes bacteria (a major bacterial group) compared to both healthy controls and IBS patients without SIBO (P values not specified for all comparisons), while healthy controls and IBS without SIBO showed no significant difference
• Lower Firmicutes levels correlated with worse abdominal pain (r = 0.436, P = 0.026) and more severe IBS symptoms overall (r = 0.494, P = 0.010)
• Lower Firmicutes levels correlated with lower defecation distress thresholds (r = 0.458, P = 0.019), indicating greater pain sensitivity during rectal balloon testing—meaning patients with less Firmicutes felt pain at lower pressure levels
• IBS patients without SIBO had significantly lower overall gut bacteria richness (diversity) than IBS patients with SIBO (P = 0.012)
• Fusobacterium bacteria were significantly less abundant in IBS with SIBO compared to healthy controls (P = 0.01), but not different between IBS groups