Gut Microbiota, Irritable Intestinal Syndrome and Dysbiosis: Pathophysiology, Medications and Perspectives on Mechanisms

Abstract

The human gut harbours a complex and diverse community of microorganisms that plays an important role in digestion, immune regulation, metabolism, and maintenance of intestinal health. A healthy gut microbiota is dominated by beneficial microorganisms, particularly anaerobic bacteria such as Faecalibacterium prausnitzii, Bacteroides, Lactobacillus, and Bifidobacterium, which contribute to the production of short-chain fatty acids and maintenance of the intestinal barrier. In inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, this microbial balance is disturbed, resulting in a condition known as gut microbiota dysbiosis. Dysbiosis is commonly associated with a reduction in beneficial anaerobic bacteria and an increase in potentially harmful or oxygen-tolerant microorganisms, including certain strains of Escherichia coli and Enterococcus. These changes may alter intestinal oxygen availability, microbial diversity, metabolite production, epithelial barrier function, and immune responses, thereby contributing to intestinal inflammation and disease progression. Increasing evidence suggests that microbial alterations may occur early in IBD and may contribute to both disease initiation and progression. This review summarizes the major changes in gut microbiota associated with IBD, discusses the mechanisms through which dysbiosis may promote intestinal inflammation, and highlights its role in disease pathogenesis. The review also discusses emerging therapeutic approaches aimed at restoring microbial balance, including probiotics, prebiotics, dietary interventions, faecal microbiota transplantation, and other microbiota-targeted strategies. Understanding the relationship between gut microbiota and IBD may provide opportunities for improved diagnosis, prevention, and development of personalised therapeutic approaches.