Adapted from episode 148 of The Perfect Stool podcast edited for readability with hist Lindsey Parsons, EdD.
What is post-infectious IBS?
Most people know what IBS is. Irritable Bowel Syndrome is a functional GI disorder characterized by symptoms like bloating, abdominal pain, diarrhea, constipation or both, often without any clear structural problem showing up on tests. It’s estimated that 10–15% of people in the U.S. have IBS, and for a significant chunk of them, their symptoms began after a bout of food poisoning or an acute gastrointestinal infection. This is what we call post-infectious IBS, which is really post-infectious SIBO or small intestine bacterial overgrowth.
You might have had some bad food, a 24-hour episode of gastroenteritis or what we often call the stomach flu, or Montezuma’s revenge you caught while traveling. You got over the fever, vomiting and acute diarrhea, but… things just never felt quite right again. Your gut developed a “new normal,” and not in a good way — with changes in bowel movements, gas, bloating, urgency and food sensitivities.
There are multiple infections that can trigger it, but the main culprits in post-infectious
IBS are:
● Campylobacter,
● Salmonella,
● Shigella and
● E. coli, (but do note that there are beneficial strains of E coli as well as
pathogenic ones)
These infections don’t just wreak temporary havoc on your gut. They can trigger long-term changes to how your intestines function. So later on in the podcast I’m going to discuss some specific research on this topic, but as a whole research has discovered that these pathogens can confuse your immune system into launching an autoimmune response.
How does food poisoning turn into an autoimmune gut disorder?
So when you get food poisoning from these 4 bacteria, your immune system makes antibodies to fight off a particular bacterial toxin present in them called cytolethal distending toxin B, or CdtB for short. But with an ongoing exposure, your immune system can get a little trigger-happy. It sees something that looks like CdtB in your own body, a protein called vinculin, which plays a role in the nerves that control gut movement, and then it starts attacking it too.
This is called molecular mimicry. In this process, the body mistakes its own tissues for invaders. The result is that you produce anti-vinculin antibodies, which damage the interstitial cells of Cajal, which are the “pacemaker cells” that keep things moving through your gut.
Without these nerves functioning properly, motility slows down or becomes uncoordinated, and you develop symptoms like bloating, constipation or alternating diarrhea and constipation. This is why post-infectious IBS is in fact SIBO. And SIBO is estimated to be the cause of IBS 60% of the time. This is more likely true in the case of loose stool or diarrhea or with a mixed presentation alternating between constipation and diarrhea, than with pure constipation, although I have seen one case of pure constipation that was post-infectious IBS.
If you’re not familiar with Dr. Mark Pimentel, he’s the executive director of the Medically Associated Science and Technology Program at Cedars-Sinai Medical Center in Los Angeles and one of the world’s leading experts on IBS and SIBO. He was the first to uncover how food poisoning can trigger long-term digestive dysfunction through an autoimmune mechanism, more specifically, how your immune system can start attacking the gut’s nerve cells after certain bacterial infections.
Because of impaired motility, bacteria entering with your food that should be swept into large intestine are never flushed into the large intestine through the cleaning waves of the migrating motor complex. So they remain in the small intestine where they ferment your food, especially fermentable fibers known as FODMAPs, and create gas, bloating, and inflammation. Think stagnant pond. This is particularly common with hydrogen-dominant SIBO, where bacteria like E. coli and Klebsiella pneumoniae tend to dominate, no matter the original offending bacteria. And if you have klebsiella pneumoniae, in addition to bloating and diarrhea, you may also experience histamine reactions, or allergic-like reactions, when eating foods with high histamine levels or that feed the klebsiella. If you want to hear more about SIBO and its subtypes, I talk about this on episode 131 for a good baseline understanding.
Dr. Pimentel’s team went one step further in investigating this. They tested the theory in reverse in animal models – injecting just the CdtB toxin (without any bacteria) and found that rats still developed SIBO and IBS-like symptoms. That was the proof they needed that the toxin itself (and the resulting autoimmune reaction) was enough to cause long-term gut dysfunction. Dr. Pimentel is also behind the development of Xifaxan (generic name rifaximin), one of the first FDA-approved antibiotics for treating SIBO. If you’ve ever been prescribed it and it wasn’t covered by insurance, you likely know about how expensive it is – the currently listed cheapest price on goodRX is $2327 for a 2-week course. I just checked and it won’t go off patent until late 2029, unfortunately. I’ll speak more later on treatments through.
How do you diagnose post-infectious IBS?
Dr. Pimentel’s lab also developed a blood test called IBS Smart, which measures anti-CdtB and anti-vinculin antibodies. Vibrant Labs also has a version of this test now, and theirs also includes candida antibodies. If you’re dealing with persistent SIBO symptoms despite treatment, these tests can help confirm whether a previous food poisoning event set off your current symptoms, which will give you clarity about whether you’re dealing with post-infectious IBS, a recent bacterial infection or just an incomplete treatment regimen. If your CdtB antibodies are elevated, your food poisoning incident was likely more recent, although these antibodies can stay elevated for years, especially if you developed post-infectious IBS. The most important question, however, is whether your vinculin antibodies are elevated. If so, this indicates that you have post-infectious IBS.
If you’re not sure whether to get the test, I generally recommend it when you have symptoms like:
● Persistent bloating, especially after meals
● Loose stools, urgency or diarrhea that lingers after an infection; or
● Alternating constipation and diarrhea
● Abdominal discomfort or cramping
● Food sensitivities, especially to high-FODMAP foods like dairy and wheat
● Sore throat, acid reflux, warmth in your chest after eating or a chronic cough
● Fatigue and brain fog (often linked to bacterial byproducts or nutrient malabsorption), and
● You have taken a round of Xifaxin or herbal antimicrobials, gotten better for a period of time, and then once again had symptoms, and you were not taking proton pump inhibitors at the time (like Prilosec or its generic, Omeprazole, or other products whose generic names end in -prazole, like Protonix, Nexium or Prevacid).
And if you’ve been listening for any length of time, you know that I have post-infectious IBS, so I can attest to the fact that this problem can last for decades, as mine started, I believe, with a food poisoning incident in Costa Rica in my mid-20’s (and I’m in my mid-50’s). I ate mayonnaise that hadn’t been properly refrigerated for a couple days and had vomiting and diarrhea for about 24 hours. Ironically, my boyfriend at the time got the same food poisoning and didn’t have any permanent issues afterwards. This is how it happens – while 9/10 people may have the same exposure, only 1/10 will develop an autoimmune reaction. I also was in Costa Rica the summer before and had a longer-term bacterial infection of some sort that I can’t recall the name of, so it could have been that one too; no way to know at this point.
So if you’re wanting some clarity on why your SIBO or IBS won’t go away, you can order the IBSsmart test online for $249, and I just noticed there’s a $100-off coupon code (IBS100, for July 2025) you can currently use.
And it looks like in addition to ordering it yourself in the US, you can also get it in Canada, Mexico, Panama, New Zealand, England, Spain, Poland and Japan, although you may need to have a doctor order it for you in other countries. One of these tests can help confirm a post-infectious IBS diagnosis, although not all practitioners are aware of or use them yet. And if you’re working with me and want to order the Vibrant Candida + IBS Profile, it’s $270 or can be part of their 3 for $700 testing deal. I’ll link to resources for that test as well in the show notes, and I know Vibrant will send tests internationally, but you have to be able to send the blood sample back in a reasonable amount of time, so there may be limitations.
How do you diagnose SIBO?
Now if you’ve never had a confirmed SIBO diagnosis, you may want to start with a SIBO breath test (which is specifically a lactulose or glucose hydrogen/methane test or a Trio-Smart test, another test developed by the Pimentel lab, which also includes hydrogen sulfide gas in it. Breath testing is the standard of care testing for gastroenterologists who are SIBO trained, but not many know about the Trio-Smart yet. Unfortunately, there are lots of ways breath testing can go wrong, and in my experience that’s usually with a false negative result (false positive results are not so much of an issue – if it’s positive, you likely have it).
First, you have to follow a very precise diet the day before of very limited foods, like rice, potatoes, 1 egg, a little bit of butter or ghee or olive oil, chicken breast or white fish, salt and pepper. Then you fast overnight for 12 hours, take an initial reading, then you have to drink a substrate mixed in water. If you can get lactulose (which is only available by prescription in the US), that’s the best option because it persists into the large intestine. And you only need to take 10 grams of it in 250-300 ml of water. If you can’t get lactulose, fructose is likely the next best option, based on tests conducted by Jason Hawrelak, ND, PhD, an Australian gut health specialist and lecturer at the University of Tasmania. But then you have to take 25 grams of fructose in the same amount of water. Otherwise, you may be sent a sample of glucose to take for the test, which is the least accurate option, and then you are supposed to take a whopping 75 grams in the same amount of water. But I discovered firsthand that this dosing might not be sent correctly. I got a test from Aerodiagnostics, and they included glucose in their kit and said to take it based on weight, which left me taking only 22 grams of it, and then I got a false negative result, wasting my time, money and effort and then my gastroenterologist closed his practice anyway.
Other ways the test can go wrong is if you don’t do the breathing into the test vials properly. You’re doing this every 15 or 20 minutes for up to 3 hours. If you have a test kit and bottles, you won’t realize if your breathing was wrong until the lab gets your results back. I have seen countless Trio-Smart reports that show multiple invalid responses, right at the important times for testing for SIBO in the small intestine (that is up to the 90 minute mark, whereas IMO and H2S SIBO can be throughout the small and large intestines). (Note that this has happened for me much more with the Trio-Smart than other SIBO breath tests because of the hydrogen sulfide addition I believe).
And finally, I just see people all the time who have all the history and symptoms to indicate either SIBO or H2S SIBO, also known as ISO (intestinal sulfide overproduction) or IMO (intestinal methanogen overgrowth, formerly known as SIBO-C for constipation), and they have a negative breath test result, and then we do a stool test and it shows the relevant bacteria or methanogens elevated.
The other option in breath testing is the Food Marble, which is an at-home breath testing device. It’s a little more than $250 if you go through me (and you can only get the clinical one through a practitioner). I’m most likely to recommend this if you have constipation because it allows me to track your progress as you eliminate methanogens in your gut, which can take multiple courses of treatment. But I still prefer stool tests as they’re generally more helpful overall, if money is an issue and you can’t order both.
How do you get rid of SIBO?
Now to talk about treatment strategies. What can you do about post-infectious IBS?
So based on 30 years of experience in dealing with this condition, I have my own methods.
First of all, I have found that periodically the bloating gets bad enough that you have to periodically just kill some bacteria. If you see a doctor, they will likely recommend rifaximin for hydrogen positive SIBO and rifaximin plus another antibiotic for IMO and bismuth (in the form of Pepto Bismol) for H2S SIBO. If you go the antibiotic route, I’d highly recommend taking 3-6 S. Boulardii probiotics a day and some form of butyrate while on antibiotics in order to protect your beneficial bacteria and prevent a candida infection. But if you have post-infectious IBS, most doctors will give up on you and you’ll give up on them before you’ve taken multiple rounds of a $2000+ antibiotic for every recurrence, so you’ll likely end up going the natural route eventually. Ideally you prevent SIBO from coming back, but without good motility, it will eventually come back. So the question is, what is the least harmful way to do this? At this point, my recommendation would be to start by trying SBI powder, or serum-derived bovine immunoglobulin powder, like the product I sell, to keep pathogens in check. A treatment dose is 5-10 grams/day; a maintenance dose is more like 2.5 grams/day. Studies have shown that it binds to pathogenic bacteria as well as to LPS (lipopolysaccride), an inflammatory endotoxin on the bodies of gram-negative bacteria like E. coli, as well as to other pathogens put off by E. coli, including CdtB. It also binds to candida, so it does double duty if you have some fungal overgrowth as we
Another antimicrobial/prebiotic option that is definitely safe for beneficial bacteria is pomegranate husk powder*, or if you’re in Australia, MediHerb pomegranate husk pills (which hopefully will be available sometime soon in the US through Standard Process). Pomegranate husk has shown antimicrobial effects against both gram positive and gram negative bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, E coli, Salmonella, Campylobacter, Listeria, Clostridium perfringens, and Pseudomonas putida as well asantifungal activity against pathogens like Penicillium expansum and Aspergillus niger. As a powder, it’s one of the most unpleasant tasting things you can imagine, and it doesn’t even mix well into a beverage, so your best bet is if you can mix it into a smoothie, or yogurt or kefir, if you tolerate them. There’s no standard dosing, but I believe Lucy Mailing recommends 1 tsp. twice/day as a treatment dose. But I’d start with ½ tsp. twice/day and see how much you can get down. A maintenance would be less. For the MediHerb pills, apparently the 300 mg pill is equivalent to 3 grams of the dried powder and they recommend 1, 2-3 times/day.
I have also experimented with using a small dose (1/2 tsp.) of MSM daily to kill off bacteria (only for SIBO or IMO, not H2S SIBO as MSM is a sulfur molecule). There is also a protocol I’ve heard about using doubling doses starting at 1/8 tsp. and getting up to 32 grams/day that I’ve experimented with a little that definitely works in terms of bringing down bloating. I was waiting to take a stool test to determine whether this killed off beneficial microbes in my gut, but have since taken stronger antimicrobials as that was all I had on hand while traveling, so my experiment was ruined. There is a little data out there in broiler chickens pointing towards MSM being good for beneficial species like Lactobacilli and harmful to E coli, but no data about whether it persists into the large intestine and its effect on more fragile species like Bifidobacteria and butyrate producers in the colon. However, given it is a powder and dissolves rapidly, I have felt it was safe enough for my purposes at a small daily dose, and I’m pretty sure that my dominant SIBO bacteria is E. coli. And it’s cheap as dirt.
If none of those work for you, the least harmful option remaining is high dose allicin for traditional SIBO or IMO (but not for H2S SIBO as garlic is a no go for people with this issue) for as short as possible a time to bring down your bloating.
Note that if you have hydrogen sulfide SIBO, there’s a whole different protocol, so you should check out my podcast number 114 for more info on that.
I also think it’s good to bring in probiotics to keep beneficial bacteria coming through to use the nutrients pathogens would otherwise ferment. There is definitely controversy over whether probiotics and in particular Lactobacilli are beneficial in SIBO, but I have found that using a relatively low dose of Seed Symbiotic for me with a meal (not at night as they recommend) does not promote bloating. On the other hand, I have had issues with yogurt, which makes me bloat, although I do okay with a couple teaspoons of sauerkraut each morning with breakfast.
And spore-based probiotics like Megasporebiotic*, Enterogermina* or Proflora 4R* should be fine, as well as Bifido only probiotics like Seeking Health’s Probiota Bifidobacterium*, Master Supplement’s TrubifdoPRO* or Ther-Biotic Bifido*, as bifidos tend to thrive in the large intestine, not the small intestine. Some people can have overgrowths of Lactobacilli in the small intestine once SIBO sets in, so if you sense a bad reaction to a probiotic or probiotic food, best to stay away from Lactobacilli-based probiotics. And probiotics with Akkermansia or other anaerobic large intestine strains like F. prausnitzii or Roseburia should also be fine, depending on what other strains they’re combined with. I discussed some of these options that are newly available in episode 141, so see those show notes for how to get ahold of those strains. And of course S. Boulardii*, which is a probiotic yeast, is also safe.
And people with histamine reactions, common with klebsiella, should be careful to choose probiotics without any histamine-producing strains in them. Seeking Health’s ProBiota HistaminX* and Vitanica’s Flora Symmetry* are two I recommend in that case.
What are prokinetics?
Then the second important element in managing post-infectious IBS is using a prokinetic, or a medication or supplement that stimulates gut motility. This isn’t motility in terms of constipation, but small intestine motility. They’re often used after antimicrobial treatment for SIBO to prevent relapse. There are only two with a clinical study, low dose erythromycin and something called Tegaserod, which I’ve never heard anyone using in the SIBO community, likely because it was removed from the market in 2007 because of possible cardiovascular risk, but re-approved in 2019 for women under 65 without cardiovascular disease. Tegaserod extended recurrence from 2 to 15 weeks to 11-58 weeks, used at a dose of 2-6 mg once at bedtime for people with constipation. And then low dose erythromycin at 50 mg at night extended recurrence to 1 to 39 weeks. I’ve heard current dosing up to 62.5 mg/night as well. These stats are a little wonky because it looks like they did some switching of groups from one treatment group to the other so there are two sets of extension times but the long and short was Tegaserod was the best of the possible treatments for preventing recurrence. I’ll link to the study in the show notes.
However, low dose Motegrity (generic name prucalopride) at 0.5-1 mg at bedtimeis what’s most often used these days by prescription. I’ve also heard people mention low-dose naltrexone 1.5-5 mg every night at bedtime as a prokinetic. Because it’s also successful in helping reduce autoimmunity, I decided to give it a try and have been on it for more than 6 months and I don’t think it’s made a difference for me, but it does make me very drowsy at night, which I like.
Herbal prokinetics are based on either ginger, or the herbal bitters formula Iberogast (now easily found in the US in a new formulation and I just discovered in both pill* as well as the original liquid* formula) or now some newer prokinetic options with orange peel or D-limonene, like MMC Restore*. Iberogast is dosed at 30-60 drops before bed. I’m not sure about the new pill formula as a prokinetic, but they recommend 1 pill before or during meals on the package of 30. Some of the ginger-based prokinetics contain a formulation called ProDigest, which is a combo of ginger that’s formulated to not produce that ginger burn effect but helps with small intestinal motility and artichoke extract, like GI Motility Complex*, which also has apple cider vinegar powder. Artichoke extract is known for helping with gastroparesis as it promotes stomach emptying. Motility Activator* is similar formulation but without the apple cider vinegar powder.
Some other ginger formulations also have 5-HTP, a precursor to serotonin, most of which is made in your gut and helps move the intestines. These may be more helpful for people with IMO because 5-HTP can lead to loose stool. The one I like in that category is Pure Encapsulation’s MotilPro*, mostly because it comes in a big bottle of 180 pills, which is helpful with suggested dosing of 3 at a time. It also has B6 and acetyl-l-carnitine in it.
Then there are a few more 5-HTP-added formulations like Prokine*, which has some additional B vitamins and lots of ingredients, so I rarely recommend that because of duplication with multivitamins and B complexes and SIBO MMC* which has extra B6 and a couple more ingredients. And finally, there’s Bio.Revive Kinetic, which is sold in the UK and Europe, and has some of the ingredients of the ayurvedic preparation triphala (known for helping constipation), as well as ginger, bitter orange and 5-HTP. It also has licorice root powder so it would be contraindicated if you have high blood pressure. All of those are linked in the show notes.
While I do recommend prokinetics to my clients and generally take one of them myself at any given time, I have never been blown away by their ability to change the general course of my condition. Even while taking them, I have always needed to periodically or regularly kill off bacteria. But they may delay how long you can go without antimicrobials, so I do recommend that you use them if you have post-infectious IBS.
What diet is best for post-infectious IBS?
I’m sure you’ve all heard of a low FODMAP diet in the context of SIBO or IBS. The biggest players in low FODMAPs are in fact wheat and dairy, and research has shown that just avoiding these two foods is about as effective as a full-on low FODMAP diet. For me, dairy is the devil. Not only am I lactose intolerant, so eating dairy leads to hot lava exiting my entrails in a most painful fashion if I don’t take lactase enzymes, but the lactose in dairy leads to the worst bloating I ever get. This is speaking from the experience of just returning from 5 weeks in Italy and eating dairy almost daily and constantly looking and feeling 6 months pregnant. In my regular life, I eat it pretty rarely and I’d recommend anyone with SIBO do the same and take lactase or a complete digestive enzyme with lactase if you do. I like a product called Lacto*.
For wheat, the issue is not in fact the gluten but rather the fructans, which are also in onions and garlic, incidentally. I have discovered over time that I personally do better with wheat than dairy by a long shot and can have a nice slice of sourdough bread with breakfast and have no bloating at all. So that’s one you can try for yourself if you don’t have gluten sensitivity or celiac. Going on a full low FODMAPs diet may be a good idea the first time you go through antimicrobials or antibiotics for SIBO, but I wouldn’t recommend living that way permanently because of the missing nutrients and fibers, in particular from beans and lentils, which support beneficial microbes. I have found that eating beans and lentils on an almost daily basis has alleviated my regular need for supplemental butyrate (I use my own Tribuytrin-Max as needed now). This has helped slow motility for me and firm up stool, and I much prefer doing that naturally to taking a pill for it. People with loose stool or diarrhea may do much better with legumes than those who have IMO.
But I do recommend using some form of tributyrin or Probutyrate* while on treatment-level antibiotics or antimicrobials for SIBO if you have loose stool or diarrhea, so as to protect the anaerobic bacteria in your colon.
What other interventions are there for curing post-infectious IBS?
So to close, there are a few other things to know about. Instead of antimicrobials, you could always go on an elemental diet. mBiota is a new option on the scene, and probably the most palatable, developed by Pimentel’s group. This is a diet with no fermentable fiber whatsoever, so it basically starves out the bacteria or methanogens. Duration is 2-3 weeks with only this liquid formula to eat.
You could also resort to a fecal transplant, but I imagine that like all the other options that change the bacteria, you’d still end up with an issue because of poor motility, so I have never recommended that course of treatment for someone with only SIBO. But if you can access it and have tried everything else, definitely do the crapsule version rather than the enema version as you want something that impacts your small intestine.
If you have constipation-dominant post-infectious IBS, then I would also recommend trying Thaenabiotic*, a formulation from human stool of everything that’s not alive, so all the post-biotic metabolites. I tried it and I would not recommend it for people with loose stool or diarrhea based on my experience.
Finally, the one big hope that I’m holding out for a cure for SIBO is fasting. In particular, the ProLon Fasting Mimicking Diet*, although you could just water fast. With ProLon your body thinks you’re fasting but you get like 500 calories/day. I have seen one report on Facebook of someone who used this diet to successfully bring down his vinculin antibodies with pre- and post-testing to prove it. This makes sense because the research on this diet shows that it helps reverse autoimmunity. As someone who needs to eat 4 times a day not to have hunger pangs, this is something I’ve dreaded trying, but I’m finally going to take the plunge. The diet has been purchased and I have booked an AirBNB in the middle of nowhere in Mexico for me and my husband in August where we can go and have no other food around us or within walking distance. So I’ll definitely report back on how that goes for me. I plan to do it again after that as I anticipate it will take several rounds, but I want to see first if I can get through 5 days, as the longest I’ve fasted before with bone broth only was short of 3 days.
Why is it important to treat and manage post-infectious IBS?
And I just want to emphasize why getting treatment for post-infectious IBS is so important. This isn’t just about mild discomfort or less than ideal bowel movements. When left untreated, post-infectious IBS usually leads to an increase in systemic inflammation from the LPS from the gram-negative bacteria, which can lead to autoimmune diseases, like Hashimoto’s in my case (although I successfully reversed that thankfully), or much more serious ones, skin conditions and food avoidance, which can lead to nutrient deficiencies and more serious problems.
The good news is that it is manageable, and you can have an enjoyable life and even eat a variety of yummy foods while having post-infectious IBS. But the sooner you identify what’s going on, the more likely you are to avoid long-term damage or complications.
If you’re dealing with gut health issues of any type (diarrhea, constipation, bloating, SIBO, IMO, H2S SIBO/ISO, IBS, IBD, gastritis, GERD, H pylori, diverticulitis, candida, etc.) or have an autoimmune disease and need some help, I see individual clients to help them resolve their digestive issues or reverse autoimmune disease naturally, You’re welcome to set up a free, 30-minute breakthrough session to see if you’d like to work with me. I also have my own two products, Tributyrin-Max, which is particularly helpful for loose stool and diarrhea as it slows your motility and firms up your stool, and SBI powder, which is an all around gut pathogen binder, which is super safe and won’t harm beneficial bacteria, and is usually the first line of treatment I educate my clients about in order to avoid stronger antimicrobial herbs.
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