Development of mucosal biofilms may be a significant feature of dysbiosis and disease among patients with irritable bowel syndrome (IBS) or ulcerative colitis (UC), according to results of a study published in Gastroenterology.

Patients who underwent endoscopy at Vienna General Hospital in Austria (n=976) or University Hospital Erlangen in Germany (n=450) were recruited for this study. A subset of patients (IBS: n=56; UC: n=25; control: n=36) provided biopsy samples for in-depth molecular and microscopic analyses.

Yellow-green biofilm layers were frequently observed in the ileal and right-colonic mucinous surfaces among patients with IBS. These films adhered tightly to the gut and could only be detached with intensive jet washing. Microscopic investigation revealed dense bacterial agglomerates.

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Biofilms were identified during 19% of all colonoscopies, specifically among 57% of patients with IBS, 34% with UC, 23% with organ transplants, 22% with Crohn disease (CD), and 6% of controls. Biofilms were observed more frequently among the German CD cohort (P =.007) and Austrian adenoma cohort (P =.036). Most frequent locations were the cecum (72%), terminal ileum (71%), ascending colon (45%), transverse colon (18%), descending colon (11%), sigmoid colon (8%), and rectum (6%).

The bacterial communities among patients with biofilms were depleted of bacterial diversity. They presented with an enrichment of the Escherichia/Shigella genus and Ruminococcus gnavus group and a depletion of short-chain fatty acid producing bacteria, such as Blautia, Coprococcus, Faecalibacterium, and Subdoligranulum.

In vitro experiments found that Escherichia coli isolates failed to spontaneously form bacterial films, but, that Ruminococcus gnavus and 5 Streptococci species were able to form the films.

Analysis of stool samples found there was a ~10-fold increase in bile acid and ursodeoxycholic acid among patients with biofilms. The study authors speculated that the accumulation of bile acids may be a possible mechanism of diarrhea.

The presence of biofilms was associated with IBS (odds ratio [OR], 19.2; 95% CI, 9.5-42.5; P £.001), UC (OR, 7.4; 95% CI, 3.7-16.2; P £.001), post organ transplant (OR, 4.3; 95% CI, 1.6-11.7; P £.01), and CD (OR, 4.2; 95% CI, 2.0-9.3; P £.001).

This study was limited by its lack of assessment of certain metabolites that have previously been associated with bacterial biofilms.

These data indicated that intestinal biofilms were identified with high-definition white light endoscopy among many patients with IBS or UC. Biofilm presence was associated with disrupted bacterial diversity and malabsorption of bile acids.


Baumgartner M, Lang M, Holley H, et al. Mucosal biofilms are an endoscopic feature of irritable bowel syndrome and ulcerative colitis. Gastroenterol. Published online June 16, 2021. doi: 10.1053/j.gastro.2021.06.024