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P672. Does the ileocecal valve functionally separate ileal and right-sided colon microbiota compositions?

N. Rossen1, S. Fuentes2, G. D'Haens1, H. Heilig2, K. Boonstra1, E. Zoetendal2, W. de Vos2, C. Ponsioen1, 1Academic Medical Center, Gastroenterology & Hepatology, Amsterdam, Netherlands, 2Wageningen University, Laboratory of Microbiology, Wageningen, Netherlands

Background

Microbe and host interaction occurs primarily along mucosal surfaces of the gastrointestinal tract. Various studies reported high inter-subject variability of a uniformly distributed microbiota in colonic biopsies sampled along the colon that differed from the feces [1,2]. The aim of the study was to investigate intra-individual differences between small and large bowel biopsies based on their microbiota composition, clustering and diversity.

Methods

We included patients scheduled for colonoscopy for diagnostic purposes. Biopsies from healthy terminal ileum and ascending colon were sampled with a standard biopsy forceps and snap frozen in liquid nitrogen. Microbiota composition based on 16S rRNA variability was determined using the phylogenetic microarray for the Human Intestinal Tract (HITChip) [3].

Results

We included 8 subjects: median age was 65 years (IQR 51–72), 7 of them were male. All patients had normal ileal and colonic mucosa. No significant differences were found in the comparison of 22 phylum/order-like and 130 genus-like groups included in HITChip analyses in ileal versus colonic mucosal biopsies. The average Pearson correlation for intra-individual comparisons was: r = 0.88±0.13. Samples clustered by host and not by sampling location (inter-individual Pearson correlation in colon and ileum samples: r = 0.88±0.04 and r = 0.87±0.06 respectively, p = 0.86), and were comparable according to: diversity, eveness and richness in colon vs ileum respectively.

Conclusion

Small and large bowel biopsies sampled from the terminal ileum or the ascending colon show similar results in clustering, diversity, evenness and richness of the host's microbiota. These findings indicate that the ileocecal valve does not separate the ileal mucosal microbiota from that of the proximal colon.

1. Eckburg et al. Science, 2005.

2. Zoetendal et al. Appl Environ Microbiol, 2002.

3. Rajilic-Stojanovic, M. et al, Environ. Microbiol 2009