Su1204 VARIATIONS OF THE MUCOSA ASSOCIATED MICROBIOTA ALONG THE HUMAN GASTROINTESTINAL TRACT IN HEALTH AND INFLAMMATORY BOWEL DISEASE

Abstract

Introduction: Very little is known about the variation in the mucosa-associated microbiota (MAM) along the human gastrointestinal (GI) tract. We aimed to determine the biogeography of the MAM along the GI tract of subjects without identifiable gastrointestinal disease, and in comparison, with Crohn's disease (CD) and Ulcerative colitis (UC) patients. Methods: Biopsies from the duodenum (DU), terminal ileum (TI), ascending colon (RC) and rectum (R) from 21 “asymptomatic control” subjects, (i.e. referred for diagnostic work-up following a positive faecal occult blood test), and 37 inflammatory bowel disease (IBD) patients (30 with UC and 7 with CD) were collected using the Brisbane aseptic biopsy device and total DNA was extracted and the 16S ribosomal RNA gene amplicon libraries were sequenced using the Illumina MiSeq platform and the quality-filtered data were processed using the Quantitative Insights into Microbial Ecology version 2 (QIIME2) software, various R packages (including Phyloseq, edgeR, and ggplot2). Bacterial load on duodenal tissue was assessed and normalised to human DNA in each sample by qPCR, using Bacteria-domain 16S rRNA gene-specific primers, and primers targeting the human beta-actin gene. Results: Compared to the control subject group, the Shannon diversity for both IBD groups was reduced at the DU and RC, and specifically, at the TI for CD patients (P<0.05); indicative of the site specificity of disease. Interestingly though, there were no differences found in the Shannon diversity of R-MAM collected from the control, UC and CD patient groups. As expected, there is a distinct separation of the DU-MAM profiles from those present at the TI, RC, and R. The most abundant genera in DU-MAM include Streptococcus and Prevotella, whereas Faecalibacterium, Bacteroides, and Blautia were among the most abundant taxa in the MAM from TI, RC, and R samples. Bacterial load on DU and TI tissue was greater for the control patients compared to the UC and CD patient groups. Conclusion: The minimal differences in the Shannon index of the R-MAM between the control, CD and UC groups, suggests it is a poor diagnostic indicator of disease. In contrast and interestingly, the alpha diversity of the DU-MAM in both the CD and UC patient groups is reduced compared to control subjects, suggestive of peripheral impacts of bowel disease on upper GI microbiota. Furthermore, the bacterial load on tissue at the duodenum and terminal ileum is reduced in both CD and UC patient groups compared to controls. More detailed assessments of these community profiles are expected to provide new insights into MAM-community dynamics in health and disease.