Max J. Schmulson, MD, Professor of Medicine, Mexico City, D.F., Mexico
Clinicians practicing in Mexico can attest to an interesting phenomenon: seeing patients with Post Infection IBS (PI-IBS) is uncommon, despite perhaps an even higher prevalence of IBS than in the rest of the world! Using Rome II criteria, the IBS prevalence in Mexico ranges from 16 to 36%, and with Rome III criteria, from 4.4 to 7.6%.
At least four small studies (using different criteria to determine the previous infectious episode) show the prevalence rates of PI-IBS in Mexico to be anywhere from 1.4% to 5.7%. To put these numbers in perspective, researchers Klem et al. recently conducted a systematic review that places the prevalence of PI-IBS at 10.1%. Although their review comprised 45 studies published from 1994 through 2015, following a total of 21,421 individuals for 3 months to 10 years for development of IBS, interestingly, no study from Latin America or Africa was identified in that review.
One may argue that the Mexican studies determine the prevalence of PI-IBS retrospectively, and this recall bias could explain the lower rates. However, the methodologies used to determine these prevalence rates are consistent with methods used by other studies in the literature. In fact, the Klem et al. review analyzed 21 out of 45 studies that determined the prevalence of PI-IBS clinically. Clearly methodology is not a factor in these differing rates
Causes of PI-IBS
Understanding conditions and prevalence for Post-Infection IBS is important because PI-IBS is currently one of the best models to study this bowel disorder of gut-brain interaction. PI-IBS was characterized by Rome Working Teams as new-onset, Rome IV criteria-positive IBS following an episode of acute gastroenteritis in patients who did not suffer from IBS prior to the infection. Furthermore, a previous infectious gastroenteritis is the best-known risk factor for developing IBS.
IBS is a multifactorial disorder, but both recent research as well as several clinical scenarios suggest a link between IBS and gut microbiota. One strong indicator from the clinical setting is that a subgroup of patients with IBS improve their symptoms with probiotics. Further, patients also show improvement with luminal antibiotics like Rifaximin that work on the microbiota of the intestinal lumen but do not affect microbiota in the tissue. In addition, imbalances of the gut microbiome (dysbiosis) that develop after systemic antibiotic use, proton pump inhibitors (PPIs) use, or small intestinal bacterial overgrowth are also related to IBS.
Hygiene Hypothesis or Disappearing Microbiome Theory?
According to the “hygiene hypothesis,” exposure to microbial-related factors early in life such as enteric infections, pet/animal contact, and sharing a bedroom may have protected this population against the development of PI-IBS. By contrast, a large population-based study from Australia, by Koloski et al., seems to suggest a more nuanced picture. They found that these factors were in fact associated with IBS in adulthood. The authors proposed that rather than the “hygiene hypothesis,” the data provided indirect support for the “disappearing microbiome theory.” This theory suggests that an impaired gut-microbiota colonization and immunoregulation early in life, due to cesarean section, shorter breastfeeding periods, maternal use of antibiotics, and formula feeding are responsible for increased prevalence of disease.
Accordingly, we are proposing that the low PI-IBS prevalence in Mexico may be due to a combination of exposure to both “non-hygiene factors” and “non-disappearing microbiome factors.” These “non-hygiene factors” are behaviors such as sharing a bedroom early in life, pet exposure, and living in rural areas. The “non-disappearing microbiome factors” could be considered as lower rates of cesarean section and gastric suctioning at birth and longer breastfeeding periods. We hypothesize that both protect against developing PI-IBS later in life, but further research is needed to confirm this hypothesis. The Rome Foundation sponsored a Global Epidemiological Study (publication forthcoming). The ongoing analysis and new research generated from our data could both shed light on the prevalence rates of PI-IBS in different parts of the world and identify risk factors.
- Barbara G, Grover M, Bercik P, et al. Rome Foundation Working Team Report on Post-Infection Irritable Bowel Syndrome. Gastroenterology 2018.
- Klem F, Wadhwa A, Prokop LJ, et al. Prevalence, Risk Factors, and Outcomes of Irritable Bowel Syndrome After Infectious Enteritis: A Systematic Review and Meta-analysis. Gastroenterology 2017;152:1042-1054 e1.
- Rivera-Lechuga D, Santana-Vargas D, Escamilla-Diego E, Charúa-Guindic L, Schmulson M. A low frequency of post infection-IBS in patients attended in a tertiary referral center in México. Rev Esp Enferm Dig. 2019;111:914-920.
- Schmulson M. Is Post Infection-Irritable Bowel Syndrome Less Frequent in Mexico? Am J Gastroenterol. 2019;114:846-848.