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P378. Bacterial colonisation of the colonic mucous gel layer: Comparative analysis of mucosal biopsies and adjacent mucous

A. Lavelle1, N. Bambury1,2, G. Lennon1, N. Docherty3, J.C. Coffey4, D.C. Winter1,2, P.R. O'Connell1,2

1UCD School of Medicine and Medical Science, Dublin, Ireland; 2Department of Surgery, St. Vincent's University Hospital, Dublin, Ireland; 3Department of Physiology, Trinity College, Dublin, Ireland; 4University of Limerick, Graduate Entry Medical School, Limerick, Ireland

Aims: In analysis of the colonic microbiome, traditional culture methods have been supplanted by molecular techniques based on highly conserved 16s rRNA pan-bacterial sequencing, allowing for enumeration of bacteria in this environment. Next generation sequencing offers new insights into the range of species and subspecies occupying the host-bacterial interface. We present a method designed to overcome difficulties with sampling throughout the colon at colonoscopy using a microbiological protected specimen brush (PSB) designed for single use which is sealed during introduction and retraction through the colonoscope to prevent cross-contamination between levels.

Materials and Methods: Consenting patients undergoing screening colonoscopy were enrolled through the endoscopy suite at St. Vincent's University Hospital, Dublin. Mucosal biopsies and adjacent mucosal brushings (using the Hobbs Medical, Inc PSB) were obtained from the right, transverse, descending and sigmoid colon. Biopsy specimens were snap frozen, cryosectioned and DNA was extracted for real-time PCR to establish bacterial signal. Adjacent mucosal brushings using the PSB were processed and DNA extracted for real-time PCR analysis.

Results: Bacterial signal was detected from specimens using both routine mucosal biopsy sampling and mucous gel brushings, suitable for comparative analysis.

Conclusion: Protected specimen brushing provides a method to sample mucous gel for bacterial analysis at different colorectal levels without the traditional problem of cross-contamination within the colonoscope. This provides a novel platform to investigate mucous gel colonisation throughout the colon and will allow for mapping of the gradient of bacterial colonisation at different loci, from luminal to crypt levels, within the host-bacterial interface.