Scientific Abstract

Proposal No.   IBD-0030
Principal Investigator:  Alexander Swidsinski, M.D., Ph.D.
Applicant Organization:  The University Hospital Charité of the Humboldt University at Berlin (Germany)
Project Title: In situ characterization of the mucosal bacterial biofilm in patients with inflammatory bowel disease using universal and group/species specific FISH probes
Period of Award:  January 1, 2003 – March 31, 2005

The non-inflamed mucosa of patients with inflammatory bowel disease (IBD) is covered with a bacterial biofilm that is absent in most control subjects.  The concentrations of mucosal bacteria are significantly related to the severity and the activity of the disease, to the patient’s age at onset of disease, treatment regimen and medical therapy.  The specific role of the mucosal flora and its precise composition remains unclear.

It has become increasingly apparent that mucosal bacteria live, develop and die in complex communities.  These communities resemble structurally and functionally a multicellular organism.  They respond in concert to environmental changes and form organized biofilms adherent to inert or living surfaces.  The multicellular structured bacteria resist antibiotics and host immune response and are more and more recognized as a significant source of disease.  Our own data strongly indicate that such communities do exist and are involved in the pathogenesis of chronic bowel inflammation.  We seek to explore the bacterial biofilm adherent to the mucosa in IBD patients.  We plan to describe the structural organization of the mucosal flora at a group and species level.  We intend to locate its components spatially in relation to each other and to the mucosal surface and to correlate the structure of the mucosal bacterial biofilm to the clinical course of the disease.  The following methods will be used.

• Selection of biopsies with high concentrations of mucosal bacteria (> 10,000 cfu/μL) from 100 IBD patients and 100 controls (irritable bowel syndrome, carcinoma, asymptomatic controls) using methods that we developed in our laboratory.
• PCR of the DNA isolated from the biopsies of interest with universal 16/23S ribosomal bacterial primer, cloning, sequencing and development of specific FISH probes with the aim to characterize 80 to 90% of the bacteria constituting the mucosal bacterial biofilm.
• In situ characterization of the structure of the mucosal bacterial biofilm using simultaneously differently stained universal and group or species-specific bacterial probes by fluorescent in situ hybridization (FISH).
• Correlation of the results with the clinical data.

A better understanding of the mucosal bacterial communities and their dynamics may revolutionize prevention and therapy of IBD.