Mo1811 Clinical Remission Induced by Exclusive Enteral Nutrition (EEN) in Pediatric Crohn's Disease Is Associated With Microbiome Metabolic Changes Toward Increased Xenobiotic Biodegradation and Metabolism

Abstract

esis of IBD, both Crohn's disease (CD) and ulcerative colitis (UC), is not well known. Most studies of human gut microbiota rely on the non-invasive collection of stool samples. However, the analysis of the fecal microbiota may not reflect the role of the mucosa-associated microbes which live in close proximity to the intestinal epithelium and that are in contact with the cells of the innate immune system directly involved in the inflammatory response. The aim of this study was to investigate the genotypes of Bacteroidetes microbiota from colon biopsies of IBD patients and to determine their relationship with the endoscopic activity of the disease. Methods: A prospective case-control study was designed. Colon biopsies from consecutive IBD patients and healthy controls (HC) (healthy subjects undergoing colonoscopy for colon cancer screening and having a healthy colon mucosa) were included. Inactive UC was defined as a Mayo endoscopic subscore of 0. Inactive CD was defined as a SES-CD score ≤ 2. Microbiota was characterized by using a restriction fragment length polymorphism (RFLP) analysis on PCR products targeting the 16SrRNA genes of Bacteroidetes digested with HinfI, PciI, DpnII and AciI. Results are shown as percentages. Results: 29 consecutive IBD patients (22 UC and 7 CD) and 15 HC were included. 8 patients presented with inactive UC (iUC) and 14 with active UC (aUC). All 7 CD patients presented with endoscopic activity (aCD). A total of 7 genotypes of Bacteroidetes called N1 and C1-C6 (of which N1 genotype is probably a strain of Bacteroides dorei and C1, and maybe C2, strains of B. vulgatus) were detected in all the biopsy samples analyzed. The number of genotypes present in biopsies from IBD patients was higher than that in HC, in whom only the N1 (66%) and C1 (34%) genotypes appear. While the presence of N1 genotypes was relatively constant in patients with active and inactive IBD, the percentage of C1 genotype in patients with aUC and aCD were very low (<5%) compared to controls. The C4 genotype never appeared in control samples and it was present in only 2% of iUC biopsies, whereas it was present in 15% and 16% of patients with aUC and aCD respectively. The C2, C5 y C6 genotypes appeared sporadically in biopsies of IBD with percentages of 1% in iUC (C2), 3% in aUC and 1% in aCD (C5), and 1% in iUC and aCD (C6), but never in HC. Conclusions: Bacteroidetes genotypes in colon biopsies differ between IBD patients and HC. These genotypes, and especially the C4 genotype, are highly specific for active IBD and further studies on their role on IBD pathogenesis are required.