As a gastrointestinal (GI) dietitian, I work with many patients with irritable bowel syndrome. For some, IBS has been a lifelong issue. For others, it comes on suddenly to wreak havoc on their lives. In the latter’s case, I pester my patients with all kinds of questions about what they ate, where they traveled, suspected food poisoning, and antibiotic use. Most report some connection with a “stomach bug” or traveler’s diarrhea. 

As it turns out, at least one in nine people (11%) who develop a GI infection, such as food poisoning, develop post-infectious IBS (PI-IBS). In PI-IBS, the symptoms did not exist before the GI infection. 

Having a GI infection is bad enough without piling irritable bowel syndrome on top. In this article, we’ll explore PI-IBS in more detail, including potential causes, risk factors, and treatment options.

Irritable bowel syndrome, a quick review

Irritable bowel syndrome is a chronic disorder of the gut-brain interaction, formerly known as a functional GI disorder. While there is no one cause of irritable bowel syndrome, we know it’s related to one or more of the following: motility disturbance, visceral hypersensitivity, altered mucosal and immune function, a physiological dysregulation of the gut-brain axis, and/or an abnormal gut microbiome. There are three main types of irritable bowel syndrome: 

• IBS-D (diarrhea-predominant) 
• IBS-C (constipation-predominant)
• IBS-M (diarrhea-constipation mixed). 

Post-infectious IBS presents as IBS-D or IBS-M. Those with IBS-C are less likely to have PI-IBS. 

Besides irregular bowel movements,  PI-IBS patients frequently report abdominal pain, cramping, bloating, excess gas, and bowel urgency. Bloating and abdominal pain are worse in patients with visceral hypersensitivity, which is a classic feature of PI-IBS. Visceral hypersensitivity is an increased sensation or perception of sensation in the intestines in response to normal or uncomfortable stimuli, such as gas, stool, or everyday moving and stretching of the GI tract.

The connection between GI infection & IBS

So, what’s the connection between a GI infection and irritable bowel syndrome? Why might one terrible acute episode lead to chronic discomfort? 

We don’t know exactly what causes PI-IBS, but it’s thought to involve a variety of factors, including ongoing inflammation, increased intestinal permeability, a shift in the gut microbiome, and altered neuromuscular function. Recent research focuses on how infectious bacteria and parasites can lead to nerve damage in the GI tract, which impairs GI motility, disrupts the gut microbiome, and can lead to a buildup of bacteria in the small intestine, a condition known as small intestinal bacterial overgrowth (SIBO). Treating SIBO can be an important step in managing PI-IBS. 

What’s remarkable is PI-IBS doesn’t always present immediately following the initial infection. It can take years to develop, so it’s important to scrutinize the patient’s timeline in search of clues. Sometimes I feel more like a detective than a dietitian. 

Not everyone who gets a GI infection will develop PI-IBS. I’ve worked with several couples who both got food poisoning, but only one of them continued to suffer a year later with PI-IBS. One’s susceptibility to developing PI-IBS depends, in part, on the health and resilience of their gut microbiome. Research has shown how dysbiosis of the gut microbiota can increase one’s risk of PI-IBS. 

Other risk factors for PI-IBS include antibiotic use, a history of anxiety or depression, and the severity of the initial GI infection. More severe infections, as evidenced by longer-lasting diarrhea, abdominal cramps, weight loss, and bloody stools, increased the risk of PI-IBS. Also, sorry ladies, but it’s more commonly seen in women. Remember those couples I mentioned? Typically, it’s the female I’m treating.

Diagnosing PI-IBS

Most often, doctors diagnose PI-IBS based on a patient’s history and presentation. If a patient meets the Rome criteria for irritable bowel syndrome and reports a recent episode of acute gastroenteritis, they’ll likely receive a diagnosis of PI-IBS. A positive stool culture test might be available, but most often it’s not. In fact, the most recent ACG Guidelines for managing irritable bowel syndrome “do not recommend routine testing for enteric pathogens, including Giardia, in all IBS patients, except those with a high pretest probability and definite risk factors for Giardia exposure.”

There is a relatively new test, the ibs-smart, which measures biomarkers in the blood to help diagnose PI-IBS. Licensed physicians can order this test to rule in PI-IBS. While this is very exciting, I have yet to see an MD order the test. 

I have PI-IBS, now what?

Fortunately, there are well-established therapies to treat IBS, whether PI-IBS or otherwise.

We’ll touch on a few of these approaches here:

Rifaximin

For drugs, I recommend PI-IBS patients speak with their physicians about rifaximin. Rifaximin is a non-absorbed antibiotic that is FDA approved for IBS-D. Some of my patients express concern over using rifaximin because it’s an antibiotic. However, studies have shown that multiple courses of rifaximin do not significantly disrupt the microbiome and the risk of developing C. difficile is low. Those who test positive for SIBO via breath testing are more likely to respond to rifaximin. 

Low FODMAP Diet 

The low FODMAP diet is a 3-phased diet scientifically and clinically proven to manage irritable bowel syndrome symptoms. FODMAPs are certain types of poorly absorbed carbohydrates (sugars and fibers) that are highly fermentable in the presence of bacteria. They can lead to uncomfortable gas, bloating, diarrhea, and other GI symptoms in some people, including those with PI-IBS or SIBO. 

The low FODMAP diet is complex and nuanced, so it’s most effective when carried out under the supervision of a knowledgeable dietitian.

Gut-Directed Psychotherapies

Since irritable bowel syndrome is a disorder of the gut-brain connection, it’s no wonder that gut-directed psychotherapies can help. 

Two popular forms of gut-directed psychotherapies include cognitive-behavioral therapy (CBT) and gut-directed hypnotherapy. A 2016 study showed gut-directed hypnotherapy to be as effective at managing IBS symptoms as the low FODMAP diet.  

Prevention

Most bouts of food poisoning happen away from the home. To reduce your risk of succumbing to Montezuma’s revenge, keep these guidelines in mind the next time you travel:

• Eat hot foods only; avoid room temperature foods. 
• Remove skins from fruits (e.g. peel an apple, choose a banana).
• Drink bottled water vs. tap water.
• Avoid ice cubes.
• Eat at clean restaurants. 
• Wash your hands well before eating.
• Avoid salad bars and uncooked vegetables.
• Avoid raw fish, undercooked meat, raw eggs, unpasteurized dairy.
• Avoid street vendors.

References

Card T, Enck P, Barbara G, et al. Post-infectious IBS: Defining its clinical features and prognosis using an internet-based survey. United European Gastroenterol J. 2018;6(8):1245-1253. doi:10.1177/2050640618779923

Lacy BE, Pimentel M, Brenner DM, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol. 2021;116(1):17-44. doi:10.14309/ajg.0000000000001036

Peters SL, Yao CK, Philpott H, Yelland GW, Muir JG, Gibson PR. Randomized clinical trial: the efficacy of gut-directed hypnotherapy is similar to that of the low FODMAP diet for the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2016;44(5):447-459. doi:10.1111/apt.13706

Thabane M, Marshall JK. Post-infectious irritable bowel syndrome. World J Gastroenterol. 2009;15(29):3591-3596. doi:10.3748/wjg.15.3591