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Could It Be PI-IBS?

Take a short quiz to find out if an antibody blood test for IBS is recommended for you.

What Is Post-Infectious IBS?

One in Nine People Who Experience Food Poisoning Develop IBS

Post-infectious irritable bowel syndrome (PI-IBS) is a form of IBS that is caused by food poisoning and can include autoimmunity. There are three main types of IBS: IBS-D (diarrhea-predominant), IBS-C (constipation-predominant), and IBS-M (diarrhea-constipation mixed). 


Post-infectious IBS almost always has a diarrheal component, with patients suffering from symptoms of IBS-D or IBS-M. If you experience IBS-C, it is less likely that you have post-infectious IBS. 


“Post-infectious IBS” simply means IBS that was caused by a food-borne gastric infection, more commonly known as food poisoning. 

Post-infectious IBS can be detected by measuring scientifically validated biomarkers in blood. These biomarkers are antibodies called anti-CdtB and anti-vinculin. To understand how these antibodies are biomarkers of IBS, it's helpful to understand exactly how food poisoning develops into IBS.





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More than 60% of IBS-D cases could
be post-infectious.

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A significant volume of research shows a clear link between food poisoning and irritable bowel syndrome (IBS), especially diarrhea-predominant IBS (IBS-D). A recent review conducted at the Mayo Clinic of over 45 studies showed that one in every nine patients who experience food poisoning develop IBS.

How Does Food Poisoning Develop into IBS?

The path from food poisoning to IBS has to do with a toxin called Cytolethal Distending Toxin B, or CdtB for short. The most common bacteria that cause food poisoning like Shigella, Campylobacter, Salmonella, and E. coli. release the toxin CdtB into your body. 

When a toxin like CdtB enters your body, your immune system fights back with an antibody - in this case, your body creates anti-CdtB. CdtB looks in some ways like vinculin, a naturally occurring protein in your body that is critical in healthy gut function. Because CdtB and vinculin can look alike, your body can think it needs to fight back against vinculin, at which point it starts producing another antibody, anti-vinculin. 

The production of anti-vinculin is an autoimmune response and leads to gut nerve damage and improper functioning of the Interstitial Cells of Cajal (ICC) and Migrating Motor Complexes (MMC). When these do not function properly, your gut microbiome is disrupted. Your gut microbiome is composed of billions of bacteria in your gut that, when balanced, keep your gut healthy.

This disruption ultimately results in post-infectious irritable bowel syndrome (PI-IBS), which presents itself as diarrhea-predominant or mixed-type (diarrhea with constipation) irritable bowel syndrome (IBS-D or IBS-M).

It's important to note that IBS can develop a long time after the initial infection. Many patients don't remember the original instance of food poisoning that may have led to IBS.

Here's an illustration of how an instance of food poisoning develops into post-infectious IBS.

How food poisoning turnsing into IBS

CdtB and Its Function in Food Poisoning.

Dr. Mark Pimentel Explains:

  • CdtB is a toxin associated with common food poisoning bacteria like Campylobacter, Shigella, Salmonella, and E. Coli.

  • CdtB enters the body through an acute infection (food poisoning), and diarrhea normally occurs immediately.

  • Classic IBS symptoms, like bloating, abdominal pain, and chronic diarrhea, may develop after one month.

How Do I Know if I’m at Risk for Post-Infectious IBS?

Anyone can develop post-infectious IBS. According to the CDC, 48 million people get food poisoning every year in America. According to a review conducted at the Mayo Clinic of over 40 research studies, 11% (1 in 9) will develop IBS. That’s about 5 million people that will develop post-infectious IBS this year in America alone. This makes food poisoning the leading known cause of IBS.


Patients with post-infectious IBS are four times more likely to contract food poisoning again. Additionally, if you do get food poisoning again, it can significantly worsen the symptoms of your post-infectious IBS.  


Post-infectious IBS presents itself as IBS-D or IBS-M. Therefore, you might have post-infectious IBS if:


  • You have chronic diarrhea, traveler’s diarrhea, or mixed diarrhea and constipation symptoms.


  • You have abdominal pain and bloating.


  • You have no other serious symptoms like blood in your stool. 


  • You have had food poisoning at some point in the past. (Note: Patients may not accurately recall whether they have had food poisoning.)

How CdtB Can Lead to Autoimmunity?

Dr. Mark Pimentel Explains:

  • CdtB shares a similar protein sequence with vinculin, a protein responsible for helping the nerves in the gut migrate and interconnect. 

  • Because CdtB and vinculin look similar, the body fights vinculin by creating anti-vinculin, resulting in autoimmunity.

  • This autoimmunity leads to damage to your gut nerves, causing your IBS symptoms.

How Do You Diagnose Post-Infectious IBS?

Diagnosing post-infectious IBS is possible with a doctor-ordered antibody blood test. The test measures the levels of two antibodies known to be elevated in the blood of patients with post-infectious IBS. The two antibodies measured are anti-CdtB and anti-vinculin.  If either antibody measures over the established threshold, then post-infectious IBS (IBS-D or IBS-M) can be diagnosed with confidence. This is why these antibodies are called biomarkers of IBS.


The only licensed antibody blood test for IBS is ibs-smart. The test was developed by Dr. Mark Pimentel and the M.A.S.T. team at Cedars-Sinai in Los Angeles, California.  ibs-smart can quickly and accurately diagnose post-infectious IBS, confirming the root cause of a patient’s IBS (food poisoning). 


Receiving a biomarker-based IBS diagnosis and an understanding that the root cause is a microbiome disruption caused from food poisoning can help your healthcare provider design a personalized treatment plan. 

How Do You Treat Post-Infectious IBS?

There are many effective, FDA-approved drugs and therapies available for post-infectious IBS (IBS-D and IBS-M), and it’s best to work with your healthcare provider to discuss your treatment options based on the complete picture of your health. 

A recent review in Digestive Diseases and Sciences examined treatment options specifically for post-infectious IBS and drew the following conclusions: 


  • Antibiotics: There are several FDA-approved antibiotics that have shown to be effective in treating IBS symptoms.

  • Diet Manipulation: Low-fermentation diets (like the Low-FODMAP diet), under the supervision of a dietician, have shown to be effective in the treatment of IBS symptoms.

  • Probiotics: More research needs to be done on the efficacy of probiotics in the treatment of IBS.

  • Fecal Transplants: Current data show that fecal transplants are not effective in treating IBS.

By accurately diagnosing your IBS and identifying the cause (food poisoning), ibs-smart can expedite your path to treatment and prevent years of potentially unnecessary procedures like colonoscopies.

You can order the test through an online prescriber or download a patient-doctor discussion guide to take to your next doctor’s appointment.

A current review in Digestive Diseases and Sciences provides an excellent overview of how gastroenteritis (food poisoning) can lead to IBS and discusses various treatment options for post-infectious IBS. Read Microbiome and Its Role in Irritable Bowel Syndrome.


Order ibs-smart Online.

No appointment necessary

You can work with a doctor online to order ibs-smart, if it’s right for you.

The online prescriber service includes: 

  • A symptoms evaluation by a doctor

  • Clear and actionable results emailed directly to you

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Prefer to work with your healthcare provider instead? Download the ibs-smart discussion guide and educational materials here



While what causes SIBO is an excess of bacteria, there are many conditions that can lead to SIBO like irritable bowel syndrome.


Diarrhea & IBS

Chronic diarrhea can indicate disorders, such as inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS).



While irritable bowel syndrome and inflammatory bowel disease share some symptoms, they are completely different illnesses. 

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