Can Food Poisoning Cause IBS? The Post-Infectious Story Behind Many SIBO Cases
Roughly one in ten people develop IBS after infectious gastroenteritis. The antibody mechanism behind it, and what a blood test can and cannot confirm.
Photo: Annie Spratt / Unsplash
Yes, it can. A single bout of infectious gastroenteritis raises the risk of developing irritable bowel syndrome roughly fourfold. About one in ten people who go through one has IBS a year later. The mechanism researchers have proposed is an autoimmune one. Your immune system builds antibodies against a bacterial toxin, and those antibodies then cross-react with one of your own gut proteins. There is a blood test for that cross-reaction. It answers less than you might hope, but it still answers something.
IBS stands for irritable bowel syndrome, which is a diagnosis made from symptoms rather than from a scan or a biopsy. When it begins after a documented infection, it gets called post-infectious IBS. This is the origin story behind a good share of the SIBO and motility cases I see. It is also the question people bring me most often, and the question is rarely what to take. It is why this happened at all.
How often this happens after an infection
A Mayo Clinic team pooled 45 studies covering 21,421 people who had been through infectious enteritis. The follow-up ran anywhere between three months and ten years. At twelve months, 10.1 percent had IBS (95% CI 7.2 to 14.1). Past twelve months the figure was 14.5 percent, with a much wider interval of 7.7 to 25.5. Risk was 4.2-fold higher in the people who had an infection in the previous year than in those who had not.
Which organism you met changes that number less than you would expect. A 2019 review of 34 studies put post-infectious IBS after salmonellosis at 12 percent and after shigellosis at 11 percent. Its authors concluded that the published literature shows similar risks across the bacterial pathogens, and that there isn't enough evidence yet to name pathogen-specific risk factors. Parasites are the outlier here. In the Mayo pooling, 41.9 percent of the people whose enteritis came from a protozoan or a parasite went on to develop IBS. After a bacterial infection it was 13.8 percent.
Travelers' diarrhea carries its own figure. Six studies pooled to a relative risk of 3.35, which is a bit over three times the risk. IBS turned up in 5.4 percent of the people who had it, against 1.4 percent of those who didn't.
Two things temper all of these numbers. There was considerable heterogeneity between the studies in the Mayo analysis, which its authors stated plainly. The risk was also not spread evenly across people. The odds ran about twice as high in women (OR 2.2), and about seventy percent higher in those who took antibiotics during the illness (OR 1.7). Anxiety, depression, and a more severe bout all carried higher odds too.
The antibody mechanism, in plain terms
Several of the bacteria that cause food poisoning make a toxin called cytolethal distending toxin B, usually shortened to CdtB. Your immune system responds to it the way it responds to any foreign protein. It builds antibodies against it.
The trouble is what those antibodies also recognize. CdtB resembles vinculin, which is one of the proteins your own cells use to anchor themselves to each other and hold their shape. In a post-infectious animal model, antibodies raised against CdtB cross-reacted with vinculin in the gut, and the animals then developed an IBS-like picture. The infection itself is usually over within a week or so. If the antibody response outlasts it, then what is driving your symptoms is no longer the infection.
The antibody story explains why symptoms start. What keeps them going is a separate problem: the migrating motor complex, the housekeeping wave that runs through the small bowel while you're not eating. When that sweep stalls, bacteria accumulate in the stretch of bowel that normally carries very few of them. Chronic stress suppresses the same sweep by a different route. One bad meal, then years of stalled cleaning waves. That is the sequence patients describe to me constantly. Until fairly recently there was no blood test for the antibody behind it.
What the blood test can and cannot tell you
The test measures two antibodies, anti-CdtB and anti-vinculin. Its validation study was large: researchers at Cedars-Sinai compared 2,375 people who had diarrhea-predominant IBS against 142 with inflammatory bowel disease, 121 with celiac disease, and 43 healthy controls. Both antibodies came out higher in the IBS group (P < 0.001).
At the cutoffs the authors settled on, anti-CdtB was 91.6 percent specific and 43.7 percent sensitive. Anti-vinculin was 83.8 percent specific and 32.6 percent sensitive. Read plainly, a positive result carries information, whereas a negative one rules out very little. Fewer than half the people with diarrhea-predominant IBS in that study tested positive. Two of that study's authors were employed by a pharmaceutical company, and the IBS participants came out of a large drug trial. That's a reason for some caution in how much weight the numbers carry, not a reason to dismiss them.
There is a second study that found the opposite. A 2024 group in São Paulo, testing 160 people in a study built around inflammatory bowel disease patients, found anti-CdtB highest in the healthy controls. Their conclusion was that neither antibody could separate IBS-D from healthy controls in that sample. A smaller Mexican series of 30 patients had found the test supportive. So this isn't settled, and the most the evidence supports is that a positive result adds weight to a diagnosis you already suspect.
What a positive result actually changes
In my practice the result changes the timeline rather than the first step. Breath testing still comes first, and the cutoff your lab uses still shapes that result. Methane-predominant overgrowth, now called IMO still needs its own approach. What a positive antibody result gives you is a reason to expect the motility work to run in months rather than in weeks, though that is my clinical impression from practice rather than a timeline any study has measured. It is also a reason to stop reading a relapse as a failed course of treatment.
That motility work is prokinetic support, meaning agents that encourage the sweep to run on schedule. Some are prescription medications and some are botanical. Which one suits you, at what strength, and for how long, belongs with the practitioner who can see everything else on your list. Which gas your breath test showed shapes that choice, along with the rest of what you take.
One more thing about a negative result, given how many people with IBS get one. It doesn't mean you invented your symptoms. With sensitivity that low, a negative test is close to uninformative on its own. The diagnosis still rests on your history and your symptoms rather than on the antibody.
If you want a structured walk-through of SIBO treatment, the SIBO Treatment Algorithm lays out the treatment options, what to do when symptoms don't improve or come back, gentler routes for people who are more sensitive, and the gut and motility repair that comes after.
FAQ
How common is IBS after food poisoning?
In a meta-analysis of 45 studies covering 21,421 people who had been through infectious enteritis, 10.1 percent had IBS at twelve months (95% CI 7.2 to 14.1). Risk was 4.2-fold higher than in people who had not had an infection in that period. The figure shifts with the organism: 41.9 percent after a protozoal or parasitic infection, against 13.8 percent after a bacterial one. The authors noted considerable heterogeneity between the studies they pooled, so read these as a range rather than a fixed rate.
What are anti-CdtB and anti-vinculin antibodies?
Cytolethal distending toxin B, or CdtB, is a toxin made by several of the bacteria that cause food poisoning. Your immune system builds antibodies against it. CdtB resembles vinculin, one of the proteins your own cells use to anchor themselves to each other, and in a post-infectious animal model the anti-CdtB antibodies cross-reacted with vinculin in the gut and produced an IBS-like picture. A blood test measures both antibodies.
Does post-infectious IBS ever go away?
For some people it does. In the pooled data, the risk of IBS was 4.2-fold higher in those whose infection was within the past twelve months and 2.3-fold higher in those whose infection was longer ago, which is consistent with some people recovering as time passes. That analysis pooled prevalence across studies rather than following individuals to recovery, so it cannot tell you the odds for any one person. The motility side of this improves with sustained work rather than on its own, which is what I see in practice rather than something a trial has followed.
Why does post-infectious IBS cause SIBO to keep coming back?
Because the antimicrobial phase clears the bacteria without restoring the sweep that keeps them from accumulating again. The migrating motor complex clears leftover food and bacteria onward into the colon while you're not eating, and when it runs poorly the small intestine cannot clear itself. Treating the overgrowth while leaving the motility problem in place is the pattern behind most of the relapses I see.
Is the IBS antibody blood test worth doing?
That turns on what you are hoping it will settle, and the clinician managing your case should weigh in before you order it. In the validation study, anti-CdtB was 91.6 percent specific and 43.7 percent sensitive, and anti-vinculin was 83.8 percent specific and 32.6 percent sensitive. A positive result carries information; a negative one rules out very little, since fewer than half the people with diarrhea-predominant IBS in that study tested positive. A 2024 study of 160 people, built around inflammatory bowel disease patients, found the antibodies could not separate IBS-D from healthy controls in that sample, so the evidence isn't settled.
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