Mucosal biofilms in ulcerative colitis

Inflammatory bowel disease (IBD) has become increasingly prevalent in the Western world. In addition, chronic intestinal inflammation is a risk factor for colon cancer. Alterations in the populations of intestinal bacteria, the microbiome, might be causally related to disease initiation and might influence disease severity. In IBD patients, the microbiome is altered, including populations of bacteria attached to the mucosal wall. These bacteria sometimes form so called biofilms, aggregates of different bacteria, similar to dental plaques. In this study, we want to investigate the composition of these bacterial biofilms and see whether they change over time (upon treatment). Patients with ulcerative colitis, a subtype of IBD, will be investigated for biofilms. Bacteria in the biofilms will be stained with a fluorescent dye and investigated with a laser endoscope. Targeted sampling allows us to identify the bacterial composition of the biofilms. This is achieved by sequencing a part of a gene present in nearly all bacteria. On the other hand, we want to look at specific bacteria (some of them are known, some new ones will be hopefully identified using the gene- sequencing approach). Here, we are interested in the bacterial localization to the mucosal wall and abundance of specific bacteria. With the use of different dyes we can stain different types of bacteria simultaneously and investigate them under a microscope. The results from this study will help us to better understand biofilm structure and may provide a disease-relevant link to ulcerative colitis.

Gastrointestinal diseases such as ulcerative colitis and irritable bowel syndrome are on the rise worldwide. Patients with such disease have an altered composition and diversity of their intestinal microbes. In this study we characterized endoscopically visible biofilms as expression of a severe imbalance of the intestinal microbiome in patients with irritable bowel disease and ulcerative colitis. We also observed such biofilms in other diseases, e.g. organ transplant patients and patients with portal hypertension. Biofilms are structured communities of microbes which can attach to surfaces such as the intestine. Using modern microscopic techniques and molecular analyses we identified the composition of biofilms and compared them to normal bacterial mucosa samples. In patients with biofilms, a higher number of bacteria can be found in the mucus and they can build a dense layer. The bacterial composition in mucosa samples and fecal samples of patients with biofilms is shifted and the microbial diversity reduced. One bacterial species, Ruminococcus gnavus is enriched in biofilms. Most probably, endoscopic visible biofilms play a central role in the pathogenesis of irritable bowel syndrome and will be of high value for diagnostics and treatment in future.