Interplay of Gut Microbiota, Biologic Agents, and Postoperative Anastomotic Leakage in Inflammatory Bowel Disease: A Narrative Review

Disruption of the microbiota resulting in pathogenicity is known as dysbiosis and is key in the pathogenesis of inflammatory bowel disease [IBD]. The microbiome of patients with IBD is characterized by depletion of commensal bacteria, in particular Bacteroidetes and the Lachnospiraceae subgroup of Firmicutes, and by the concomitant increase in Proteobacteria and the Bacillus subgroup of Firmicutes. These changes reflect a decrease in microbial diversity with a concomitant decrease in health-promoting bacteria like Faecalibacterium and Roseburia. Treatment with biologic agents has changed the natural course of disease, improving patient outcomes. Changes in gut microbiota occur under treatment with biologic agents and act towards reversal of dysbiosis. These changes are more striking in patients achieving remission and specific gut microbiota signatures may be predictive of treatment response and a step towards precision medicine, since, despite advances in medical treatment, some patients are at risk of surgery and subsequent complications such as anastomotic leakage. This review summarizes current available evidence on the interplay of gut microbiota and biologic agents, surgery, and surgical complications in patients with IBD.