P785 Association of Bacteroidetes with endoscopic activity in patients with inflammatory bowel disease

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Background: The role of gut microbiota on the etiopathogenesis of inflammatory bowel disease (IBD), both in 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. Mucosa-associated germs live in close proximity to the intestinal epithelium and 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 single-center, observational cross-sectional study was designed. Consecutive patients with Crohn's disease (CD) and ulcerative colitis (UC) who attended the Endoscopy Unit for colonoscopy were included. Colonic biopsies were taken to characterize microbiota. We did this 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.

Inactive UC was defined as a Mayo endoscopic score of 0. Inactive CD was defined as a SES-CD ≤2. The association of endoscopic activity with demographic (gender, age and smoking habits) and analytical (VSG, PCR and platelets) factors was also evaluated. The results were expressed as prevalence and analyzed using logistic regression.

Results: 52 consecutive IBD patients (28 CD and 24 UC) were included. 33 patients showed endoscopic activity of the disease (20 CDa and 13 UCa). A total of eight genotypes of Bacteroidetes called N1, C1-C5, CB 10 and CB13 were detected. N1 is probably a strain of Bacteroides dorei, and C1 and C2 B.vulgaris strains. While the presence of N1 and C1 genotypes was consistent in patients with active and inactive IBD, the percentage of C4 genotypes in patients with UCa and CDa was very high (81.8%) compared to patients without activity (36.8%) (p=0.001). C3 genotype was observed in 4/19 inactive IBD patients and in 12/33 of active IBD patients (p=0.24). Other genotypes were found sporadically in IBD biopsies. No differences were observed between the genotype of patients with CD or UC. After multivariate analysis, C4 genotype in colon biopsies was associated with endoscopic activity of the disease (OR 8.58, 95% CI 2.16–34.08) (p=0.02).

Conclusions: The presence of genotype C4 of Bacteroidetes is associated with the endoscopic activity of IBD, in both CD and UC. Future studies are needed to determinate their role as an activity biomarker.

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