Available at: https://digitalcommons.calpoly.edu/theses/543
Date of Award
MS in Biological Sciences
Dr. Christopher Kitts, PhD
In severe cases of ulcerative colitis (UC) unresponsive to current treatment options, patients require a complete proctocolectomy, or surgical removal of the colon. Ileal pouch anal anastomosis (IPAA) has become the preferred surgical technique for patients who require surgery, as this method restores rectal function. This procedure is also used to treat colorectal cancers such as adenocarcinoma and familial adenomatous polyposis (FAP). The surgery involves an abdominal colectomy with the construction of an ileal pouch created from folded tissue recovered from the ileal portion of the small intestine. Up to 50% of patients who require IPAA surgery experience an episode of pouchitis, a non-specific inflammation of the constructed ileal pouch with unknown etiology. Several hypotheses have been proposed regarding the pathogenesis of pouchitis. Current theories include bacterial overgrowth due to fecal stasis, microbial imbalance (dysbiosis), immune alteration, genetic susceptibility, metaplasia, ischemic complications of surgery, a recurrence of UC, or even a novel form of inflammatory bowel disease. The efficacy of antibiotics and probiotics in treating pouchitis and maintaining remission underscores the importance of gut microbiota in the development of this condition. In the study, we aimed to characterize the intestinal bacterial communities that inhabit IPAA pouches of both UC and FAP patients, in an effort to investigate the hypothesis that bacterial dysbiosis is involved in the pathogenesis of pouchitis. Mucosal biopsy and stool samples were analyzed from patients with UC and pouchitis (UCP), healthy UC controls (HUC) and healthy pouches with a background of FAP (FAP). Samples were examined through analysis of terminal restriction fragment length polymorphisms (TRF) and DNA sequencing. The data presented here demonstrate that a microbial imbalance exists in pouchitis, as bacterial communities in pouchitis differ significantly from healthy UC pouches and pouches constructed for FAP. Both methods identified potential groups of organisms that may play a role in the development of pouchitis, including decreases in protective Lactobacillus and Bacteroides and increases in mucin-degrading Clostridium and Akkermansia. A better understanding of the factors driving the pathogenesis of pouchitis will not only benefit patients with this disease, but also lead to a better understanding of the complex relationship that exists between the human host and the diverse community of organisms that inhabit the gastrointestinal tract.