Das Wachstums- und Sporulationsverhalten klinischer Clostridioides-difficile-Isolate unter intestinalen Gallensalzkonzentrationen

Impact of intestinal bile acids on germination and sporulation of clinicila Clostridioides difficile isolates

by Elif Yilmaz
Doctoral thesis
Date of Examination:2021-12-14
Date of issue:2021-11-10
Advisor:Prof. Dr. Uwe Groß
Referee:Prof. Dr. Uwe Groß
Referee:Prof. Dr. Volker Ellenrieder
Referee:Prof. Dr. Ralf Dressel
Persistent Address: http://dx.doi.org/10.53846/goediss-8938

 

 

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Abstract

English

Problem: Clostridioides difficile infections (CDI) have emerged as the leading cause of hospital-acquired diarrhea. The disruption of physiological gut microbiota by consumption of antibiotics is one of the major risk factors for CDI. After oral uptake of metabolically inactive spores, bile acids within the gut impact the germination and outgrowth of C. difficile. Previous studies have shown that under standardized concentrations of 0.1 %, CDCA, LCA, and DCA (summarized here as “BAIF”) can inhibit the growth of C. difficile. The importance of the healthy gut microbiota to prevent CDI is well-known, assuming that gut microbiota prevent the outbreak of CDI by influencing bile acid-proportions within the intestine. However, intestinal bile acid proportions differ from the standardized 0.1 % concentrations.  We therefore investigated the role of physiological bile acid concentrations and inter-strain variability in the development of a CDI.  Methods: In order to determine inter-strain variability, a total of 23 clinical isolates of different ribotypes, toxinotypes, and origin, covering isolates of all five  clades, were tested. To analyze spore germination and growth kinetics of C. difficile under a) intestinal, b) fecal and, c) standardized 0.1 % bile acid concentrations, the optical density at 600 nm was measured using wellplates and the hungate technique. The induction of sporulation was tested for eight  clinical isolates by counting the CFU/ml using sporulation assays.  Results: Bile acids with inhibiting function at 0.1% concentration (BAIF) did neither prevent spore germination nor outgrowth of C. difficile strains when tested at intestinal concentrations, suggesting that intestinal concentrations of BAIF have only marginally effect on C. difficile. Analyzing the sporulation, intestinal concentrations of BAIF had little influence on sporulation and only fecal concentrations inhibited vegetative growth and sporulation of C. difficile. 
Keywords: C. difficile; bile acids; sporulation; intestinal concentration; growth
 
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