Role of Intestinal Microbiota in Ulcerative Colitis – Effects of Novel Carbohydrate Preparations

Louise Kristine Vigsnæs

Research output: Book/ReportPh.D. thesis

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The microbiota of the human intestinal tract is complex with variable populations of bacteria who
are either permanent gut residents (commensal bacteria) or transient inhabitants introduced from
the environment. The commensal bacteria are believed to be important for human health due to
actions such as protection against pathogens, induction of immune regulatory functions and
nutrient processing. Hence, the composition of commensal bacteria is important to preserve
colonic health.
Ulcerative colitis (UC) is an inflammatory bowel disease and dysbiosis in the composition of
commensals has been reported, which could affect colonic health. In the experimental part of this
thesis, the fecal microbiota derived from UC patients in either remission or with active disease and
healthy subjects was quantified using quantitative Real‐Time PCR (qPCR) to examine the
microbiota composition. The results demonstrated that the microbiota composition was different
in UC patients in relapse compared to healthy subjects and the difference could be ascribed Gramnegative
bacteria, hence indicating that an altered microbiota composition is associated with
colonic inflammation. Additionally, results revealed that the microbiota composition in remission
either resembled the composition in healthy or in relapse, demonstrating that the microbiota in
remission is unstable.
The mucus layer lining the epithelium of the intestinal tract is important for the protection of the
epithelium in humans. The commensal bacteria that colonize the colonic mucus are suggested to
play an important role in stimulating regulatory immune responses compared to luminal bacteria,
since they reside closer to the intestinal epithelial cells. The ability of fecal microbiota derived
from healthy subjects and UC patients to colonize mucus was examined in a study of this thesis to
elucidate, if the adhesion capacity is different depending on disease state. For this purpose, an in
vitro dynamic gut model was used. Several bacterial taxa from both lumen and mucus were
quantified using qPCR. The results revealed that the bacterial community of the mucus differed
from that of the lumen and that lactobacilli and bifidobacteria derived from UC patients had a
significant decreased capacity to colonize mucus than observed for similar bacterial groups
originating from healthy subjects. This suggests that the inflammatory state in UC may influence
the adhesion capacity of commensal bacteria such as beneficial Gram‐positive bacteria lactobacilli
and bifidobacteria.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages195
Publication statusPublished - 2011


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