Scientific Abstract

Proposal No. IBD-0240R2
Principal Investigator: Paris Tekkis, M.D. 
Applicant Organization: Imperial College of Science, Technology and Medicine (London, England)
Project Title: Investigation of the bacterial pathogenesis of inflammation of the ileal reservoir following restorative proctocolectomy for ulcerative colitis and familial adenomatous polyposis 
Award Period: April 1, 2009 – September 30, 2010

Restorative proctocolectomy with ileal pouch-anal anastomosis is the procedure of choice for patients with ulcerative colitis who require surgery. Up to 50% of patients develop pouchitis causing significant morbidity. A bacterial dysbiosis is thought to be fundamental in the pathogenesis of pouchitis and other forms of inflammatory bowel disease although this is unproven. Many of the bacteria found within the human gut microbiota are unculturable and cannot be identified with conventional techniques. Newer molecular approaches based on bacterial 16S rRNA sequencing permit the identification of such bacteria. This study will identify, compare and contrast the mucosal-adherent microbiota present in both pouchitis and non-pouchitis pouches in patients with both ulcerative colitis (UC) and familial adenomatous polyposis (FAP).

Mucosal adherent bacteria will be studied using bacterial ribosomal small subunits (16S rRNA) genes as a target. Bacterial rRNA will be extracted from pouch biopsies and 16S gene amplified by polymerase chain reaction (PCR), using broad range primers. Clone libraries will be established from each sample and ~250 clones from each library sequenced. The resultant sequence files will be compared to the National Center for Biotechnology Information (NCBI) BLAST database to identify the microbial populations. We will also determine by immunostaining any changes of the adhesion molecules and tight junction proteins in frozen section tissues from pouchitis, FAP and control patients and potentially correlate with the changes in the mucosal microbial population.

This study will aim to identify the individual bacterial species present in the pouch mucosa and confirm or refute the dysbiosis theory of IBD. If proven it should allow new specific antibiotic or probiotic therapies to be developed for the treatment of pouchitis. It should also have important implications in our understanding of the pathogenesis of both ulcerative colitis and Crohn’s disease.