In this study published in the journal Gastroenterology, Baumgartner et al recruited 1426 patients with irritable bowel syndrome (IBS) and ulcerative colitis who underwent endoscopy at the Vienna General Hospital in Austria or the University Hospital Erlangen in Germany to investigate the presence of mucosal biofilms that could be seen on endoscopy. A subgroup of 117 patients was selected for the microscopic and molecular analyses of these biofilms using 16S-rRNA gene amplicon-sequencing, confocal microscopy, scanning electron microscopy and metabolomics.

Fifty-seven percent patients with IBS, 34% of patients with ulcerative colitis, 23% with organ transplants and 22% with Crohn disease and 6% of controls were found to have yellow-green adherent layers in the ileum and right colon visible on high-definition white light endoscopy, which were confirmed to be bacterial biofilms on microscopy. They were most commonly found in the cecum (72%) followed closely by the terminal ileum (71%). Biofilms were also detected in the ascending colon (45%), transverse colon (18%), descending colon (11%), sigmoid colon (8%) as well as the rectum (6%).

A correlation between the biofilms and gut dysbiosis was found on 16S-sequencing. Seventy-one percent of patients with biofilms showed decrease in bacterial diversity with abundant growth of Escherichia coli and/or Ruminococcus gnavus. Bile acids were detected within the biofilms on metabolomic analysis linked to increased excretion of bile acids in stool, which were suggestive of bile acid malabsorption as a mechanism of diarrhea.

The study concluded that mucosal biofilms are a significant endoscopic feature of IBS and ulcerative colitis along with intestinal dysbiosis and disturbed bile acid metabolism. Further, it implicates biofilms in the pathophysiology of these intestinal diseases. The authors write, “Biofilms represent a new dimension in understanding GI health and disease and hold the potential to revolutionize diagnostic algorithms and treatment approaches in functional GI disorders.”

Baumgartner M, et al. Gastroenterology. 2021 Oct;161(4):1245-1256.e20. doi: 10.1053/j.gastro.2021.06.024.