Certain strains of Escherichia coli bacteria, known as AIEC, are found in people with Crohn’s disease but not in those with irritable bowel syndrome. These bacteria attach to specific receptors in...
Mechanism
Synthesis from 1 study
Crohn’s disease happens when a specific type of E. coli gets stuck in the gut lining of people with certain genes, hides inside immune cells, and won’t get cleaned up, causing long-term swelling. Irritable bowel syndrome doesn’t involve this bacteria or this kind of damage—it’s caused by other gut...
Most probable mechanism
In people with certain genetic mutations, a specific type of E. coli bacteria sticks to the gut lining using a protein that’s overproduced there, gets inside the cells, and hides inside immune cells called macrophages. Inside these immune cells, the bacteria avoid being destroyed because the cell’s cleanup system doesn’t work properly due to the same genetic mutations. The bacteria multiply inside, trigger constant low-level inflammation, and damage the gut lining over time, leading to chronic disease.
Adherent-invasive Escherichia coli binds to CEACAM6 receptors overexpressed on ileal epithelial cells
The bacteria invade epithelial cells and transcytose across the intestinal barrier into the lamina propria
Bacteria are phagocytosed by macrophages but evade destruction by impairing autophagy due to ATG16L1 and NOD2 genetic variants
Intracellular bacterial proliferation forms persistent bacterial communities within macrophages
Persistent intracellular bacteria activate sustained pro-inflammatory signaling, leading to chronic mucosal inflammation and tissue damage
Less supported by current evidence, but not ruled out
In irritable bowel syndrome, different gut bacteria produce chemicals like hydrogen sulfide or methane that directly irritate nerve endings in the gut wall or slow down intestinal movement, causing pain or constipation without damaging the tissue.
H2S-producing bacteria increase in abundance and release hydrogen sulfide, which activates TRPA1 receptors on visceral sensory nerves
Hydrogen sulfide increases paracellular permeability and sensitizes nerves, leading to abdominal pain and diarrhea
Methanogenic archaea produce methane, which directly inhibits intestinal smooth muscle contraction
Reduced motility causes stool retention and constipation-predominant symptoms
After a severe gut infection, the immune system makes antibodies that mistakenly attack a protein in the gut’s nerve network, damaging the cells that control gut movement and leading to long-term bloating, constipation, or diarrhea.
Infection by certain bacteria triggers antibody production against a bacterial toxin
These antibodies cross-react with a similar human protein (vinculin) found in enteric neurons and pacemaker cells
Autoimmune damage to interstitial cells of Cajal and enteric neurons disrupts the migrating motor complex
Loss of coordinated gut contractions causes bacterial overgrowth and chronic motility symptoms
In irritable bowel syndrome, the gut lining becomes slightly leaky, allowing bacterial parts to enter the tissue and trigger mild, ongoing immune activation without visible damage, which sensitizes nerves and alters gut movement.
Increased intestinal permeability allows microbial components like LPS and flagellin to cross the epithelial barrier
These components bind to Toll-like receptors on immune cells, activating NF-kB signaling
Low-level cytokine production and mast cell activation sensitize visceral nerves without causing tissue destruction
Evidence from Studies
Supporting (1)
Community contributions welcome
Gut Microbiota in Irritable Bowel Syndrome and Inflammatory Bowel Disease: Differences in Pathophysiology, Biomarkers, and Treatment Implications
Contradicting (0)
Community contributions welcome
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