Background and aims: Crohn's disease is associated with alterations in the gut microbiome and metabolome described as dysbiosis. We characterized the microbial and metabolic consequences of ileal resection, the most common Crohn's disease surgery.
Methods: Patients with and without intestinal resection were identified from the Diet to Induce Remission in Crohn's Disease and Study of a Prospective Adult Research Cohort with Inflammatory Bowel Disease studies. Stool samples were analyzed with shotgun metagenomics sequencing. Fecal butyrate was measured with 1H nuclear magnetic resonance spectroscopy. Fecal bile acids and plasma 7α-hydroxy-4-cholesten-3-one (C4) was measured with mass spectrometry.
Results: Intestinal resection was associated with reduced alpha diversity and altered beta diversity with increased Proteobacteria and reduced Bacteroidetes and Firmicutes. Surgery was associated with higher representation of genes in the KEGG pathway for ABC transporters and reduction in genes related to bacterial metabolism. Surgery was associated with reduced concentration of the But gene but this did not translate to reduced fecal butyrate concentration. Surgery was associated with decreased abundance of bai operon genes, with increased plasma C4 concentration, increased primary bile acids and reduced secondary bile acids, including isoLCA. Additionally, E lenta, A equalofaciens and G pamelaeae were lower in abundance among patients with prior surgery in both cohorts.
Conclusions: In two different populations, prior surgery in Crohn's disease is associated with altered fecal microbiome. Patients who had undergone ileal resection had reduction in the potentially beneficial bacteria E lenta and related actinobacteria as well as secondary bile acids, including isoLCA, suggesting that these could be biomarkers of patients at higher risk for disease progression.
Keywords: Crohn’s disease; bile acids; butyrate; dysbiosis; microbiome.
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