Is the microbiome the answer to inflammatory bowel disease: systematic review

Area of Science:

• Gastroenterology
• Microbiome Research
• Immunology

Background:

• Inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), has an unknown pathogenesis.
• Genetics, environmental factors, and the gut microbiome are implicated in IBD.
• Gut dysbiosis is a feature of IBD, but its precise role remains unclear.

Purpose of the Study:

• To review and synthesize findings from observational studies on the gastrointestinal microbiome in IBD patients compared to healthy controls (HC).
• To identify specific alterations in microbial diversity and composition associated with IBD.

Main Methods:

• A systematic literature search of Medline and Embase was conducted up to January 2025.
• Included studies compared IBD patients (faecal, mucosal biopsy, saliva, or oral swab samples) with HC.
• Excluded studies with <10 IBD patients, without HC comparison, or with confounding factors like infections or medications.

Main Results:

• Most of the 83 studies reported reduced alpha and beta diversity in IBD, particularly in CD.
• Depletion of beneficial butyrate-producing Firmicutes (e.g., Faecalibacterium prausnitzii) and decreased Bacteroidetes were observed in IBD.
• Increased Proteobacteria and Enterobacteriaceae were noted in IBD patients.

Conclusions:

• The gut microbiome in IBD is characterized by reduced biodiversity, more pronounced in CD, with an increase in pathogenic bacteria and a decrease in beneficial ones.
• Significant associations between the microbiome and IBD were identified.
• The exact mechanisms driving these associations, including causality and interplay with host immunology, require further elucidation.