Link between intestinal microbiota and irritable bowel syndrome (IBS)
Post-infectious irritable bowel syndrome is related to a lasting change in the gut microbiota diversity which promotes intestinal permeability, inflammation and enteric nervous system disturbances.
Post-infectious irritable bowel syndrome (PI-IBS) occurs in around 10% of cases after an episode of bacterial or viral infectious gastroenteritis. It presents as chronic diarrhea and abdominal pain that may persist for several months, or even years. It is associated with major alterations in the intestinal microbiota whose understanding could facilitate the prevention of this complication and improve patient care. An American team carried out a literature review to study the links between the severity of a gastrointestinal infection, psychiatric co-morbidities, intestinal microbiota and PI-IBS. The researchers have observed that the more severe the infection (gastroenteritis), the greater the risk of PI-IBS, especially in patients with co-morbidities such as anxiety or depression. These links depend, among other factors, on the intestinal microbiota composition.
Microbiota diversity significantly decreases during an infectious episode and even more if the episode is severe and promotes local inflammation, alterations in the intestinal barrier and enteric nervous system stimulation. These anomalies persist in case of PI-IBS, with a lasting increase in Bacteroidetes and Proteobacteria, and a decrease in Firmicutes and Clostridia. They are associated with a drop in short-chain fatty acid production and they promote intestinal hyperpermeability, local and systemic inflammation (with increased release of interleukins IL-6 and IL-1β and pro-inflammatory cytokines), and permanent stimulation of the enteric nervous system, thus generating visceral pain and increased bowel motility.
The role of the intestinal microbiota should, however, be analyzed together with individual genetics, immunity and visceral sensitivity. That is why, further work is required to clarify these interactions and contemplate the use of certain probiotics.
Downs I et al. Post infection irritable bowel syndrome: The links between gastroenteritis, inflammation, the microbiome, and functional disease. J Clin Gastroenterol. 2017 Nov/Dec;51(10):869-877.