Post-Infectious IBS and SIBO
Researchers first reported in a 1962 study that 25% of patients suffering from IBS reported that the onset of their IBS was when they came down with a case of dysentery. (1). In another research study, 20 out of 75 patients suffering from acute gastroenteritis had persistent symptoms of IBS as long as 6 months after their episode of diarrheal disease. (2)
Infectious gastroenteritis is the most significant risk factor for IBS, it has been found that the risk of developing IBS increased six-fold after having an acute gastrointestinal infection, such as food poisoning, travellers’ diarrhea, or gastroenteritis. (3)
Studies have revealed that post-infectious IBS (PI-IBS) develops in certain people who have had bacterial gastroenteritis brought on by several enteric pathogens like Campylobacter species, Shigella, Salmonella, E.coli and certain viruses. (4,5,6)
What all of these bacteria have in common is that they all produce a substance called cyto-lethal distending toxin (CDT). CDT causes cell cycle arrest and apoptosis of intestinal cells (7.8)
For most of us, when our gastrointestinal tract is exposed to CDT, our gut’s immune system produces an anti-CDT antibody and we begin to neutralize the toxin and start to recover from the infection. However, 1 in 5 of us will have an autoimmune cross-reaction and as we produce an anti-CDT antibody, we also produce an anti-vinculin antibody. Vinculin is a protein that connects the Interstitial Cells of Cajal (ICC) together within the smooth muscle of the small intestines. The ICC are electrical pacemaker cells that initiate the migrating motor complex (MMC) via electrical stimulation.
The Migrating Motor Complex (MMC)
The MMC is a ‘cleansing wave’ of high-frequency contractions of the smooth muscle of the GI tract, that moves indigestible food particles from the small intestine into the colon. This process occurs about every 90 to 120 minutes. When you hear the “growling” sound in your belly this is your migrating motor complex at work.
The MMC doesn’t just sweep food waste into the large intestine, but it also sweeps the small intestines clean of bacteria every 3 – 4 hours throughout the day. This is how our body naturally keeps 98% of our gut bacteria in our large intestine and only 2% of our gut bacteria in our small intestine, therefore preventing bacterial overgrowth in the small intestine..
If you are the 1 in 5 who produce an anti-vinculin antibody after a case of food poisoning or traveler’s diarrhea, your immune system ends up attacking the connections between the ICC. Because the ICC works as an electrical circuit, when the vinculin proteins are destroyed by our own immune cells, the MMC begins to become less and less effective, and eventually can not continue to sweep the small intestines clean of bacteria. Over time, bacteria can then overpopulate the small intestines, and SIBO is the result.
Research at Cedars-Sinai found that people with IBS experience cleansing waves 70% less often, compared to people without IBS. (9)
In summary, the sequence of events leading to post-infectious IBS and SIBO looks like this:
- During an episode of food poisoning, pathogens such as C. jejuni release CDT-B into the gut lumen.
- The immune system recognizes CDT as foreign and creates antibodies to it. Anti-CDT antibodies proliferate.
- Anti-CDT antibodies cross-react with vinculin that is present in the gut, leading to the production of anti-vinculin antibodies. (10)
- Anti-vinculin antibodies destroy vinculin, disrupting epithelial tight junction proteins and damaging nerve cells. This causes leaky gut and dysmotility. Faulty intestinal motility facilitates small intestinal bacterial overgrowth (SIBO) and triggers IBS symptoms. (11)