14 • Probe •Vol LXII • No. 4 • Sep–Dec 2023 Altered Gut Microbiota and Irritable Bowel Syndrome The gut microbiota that typically begins to colonize at birth, matures during the first 3 years of life. The gut is inhabited by more than 2000 different bacterial species of Bacteroidetes, Firmicutes, Actinobacteria, and Proteobacteria phyla.1 Healthy gut microbiota is essential for proper functioning of the gastrointestinal (GI) tract and is affected by factors such as dietary habits, smoking, anxiety, depression, and recurrent antibiotic treatments. A shift in the gut microbial diversity (gut dysbiosis) leads to the colonization of opportunistic pathogens. Several systemic studies have highlighted that the decreased abundance and diversity of the gut microbiota may increase the severity of irritable bowel syndrome (IBS) symptoms.1 IBS is one of the most common GI diseases that manifests as abdominal pain, bloating, and mixed bowel movements of diarrhea and/or constipation. The pathophysiology of IBS is intricate and multifactorial. Alterations in the gut–brain axis, abnormalities in the gut endocrine cells and the enteric nervous system, visceral hypersensitivity, GI dysmotility, postinfection status and low-grade inflammation, malabsorption of carbohydrates, and altered gut microbiota composition are found to influence IBS.1 Influence of the Gut Microbiota on GI Health Diminished fecal microbial diversity and altered gut flora in patients with IBS suggest a causal involvement in the development and recurrence of IBS.2 Studies confirm that the fecal microbiota in patients with IBS differs significantly from that in healthy individuals, and it potentially contributes to alterations in bowel habits and affects colonic transit. The gut metabolome, intestinal permeability, and inflammatory pathways have also been suggested to play a role in microbiota-related GI diseases.3 Gut microbiota signatures of IBS Reduced diversity of the gut microbiota and presence of Clostridium, Prevotella, and methanogenic bacterial species are considered as IBS-specific microbiome signatures that associate with the severity of symptoms.3 Postinfection IBS, small intestine bacterial overgrowth, stress, antibiotics, diet, and early childhood feeding and hygiene practices influence the gut microbiota and affect the incidence rate of IBS. A gut microbiota analysis suggested a doubled ratio of Firmicutes to Bacteroidetes; abundance of Dorea, Ruminococcus, and Clostridium species; and fewer Faecalibacterium species in patients with IBS compared with that in healthy controls.4 The Importance of Prebiotics and Probiotics Pre- and probiotics are nonpharmacologic recommendations for reducing the symptoms and severity of IBS. Consumption of prebiotics provides essential nutrients to enhance the growth of beneficial bacteria and deters the pathogens in the bowel. Consumption of probiotics can normalize the interaction between pro- and anti-inflammatory cytokines; stabilize the microbiota; and reduce visceral sensitivity, intestinal permeability, and inflammation.1,2 References 1. Mazzawi T. Microorganisms. 2022;10(7):1332. 2. Sharma S, et al. Cureus. 2023;15(3):e36565. 3. Ghaffari P, et al. J Transl Med. 2022;20:173. 4. Olyaiee A, et al. Front Med. 2022;9:890127.
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