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Assessing the Viability of a Synthetic Bacterial Consortium on the In Vitro Gut Host-microbe Interface
Published on: July 4, 2018
Bacillus cereus NVH 0500/00 Can Adhere to Mucin but Cannot Produce Enterotoxins during Gastrointestinal Simulation
Varvara Tsilia1, Frederiek-Maarten Kerckhof2, Andreja Rajkovic3
1Laboratory of Microbial Ecology and Technology (LabMET), Department of Biochemical and Microbial Technology, Ghent University, Ghent, Belgium Laboratory of Food Microbiology and Food Preservation (LFMFP), Department of Food Safety and Food Quality, Ghent University, Ghent, Belgium.
Abstract:
Adhesion to the intestinal epithelium could constitute an essential mechanism of Bacillus cereus pathogenesis. However, the enterocytes are protected by mucus, a secretion composed mainly of mucin glycoproteins. These may serve as nutrients and sites of adhesion for intestinal bacteria. In this study, the food poisoning bacterium B. cereus NVH 0500/00 was exposed in vitro to gastrointestinal hurdles prior to evaluation of its attachment to mucin microcosms and its ability to produce nonhemolytic enterotoxin (Nhe). The persistence of mucin-adherent B. cereus after simulated gut emptying was determined using a mucin adhesion assay. The stability of Nhe toward bile and pancreatin (intestinal components) in the presence of mucin agar was also investigated. B. cereus could grow and simultaneously adhere to mucin during in vitro ileal incubation, despite the adverse effect of prior exposure to a low pH or intestinal components. The final concentration of B. cereus in the simulated lumen at 8 h of incubation was 6.62 ± 0.87 log CFU ml(-1). At that point, the percentage of adhesion was approximately 6%. No enterotoxin was detected in the ileum, due to either insufficient bacterial concentrations or Nhe degradation. Nevertheless, mucin appears to retain B. cereus and to supply it to the small intestine after simulated gut emptying. Additionally, mucin may play a role in the protection of enterotoxins from degradation by intestinal components.
Insights
Bacillus cereus adheres to intestinal mucin, potentially aiding its survival and transport through the gut. Mucin may also protect bacterial toxins from degradation in the intestines.
Area of Science:
- Microbiology
- Gastroenterology
- Food Science
Background:
- Intestinal adhesion is a key factor in Bacillus cereus pathogenesis.
- Mucin glycoproteins in the gut lining protect enterocytes and can serve as bacterial nutrient and attachment sites.
Purpose of the Study:
- To investigate the in vitro adhesion of Bacillus cereus to mucin under simulated gastrointestinal conditions.
- To evaluate the stability of nonhemolytic enterotoxin (Nhe) when exposed to intestinal components in the presence of mucin.
Main Methods:
- In vitro exposure of Bacillus cereus to low pH and intestinal components (bile, pancreatin).
- Mucin adhesion assay to determine bacterial attachment and persistence after simulated gut emptying.
- Investigation of Nhe stability on mucin agar.
Main Results:
- Bacillus cereus grew and adhered to mucin during in vitro ileal incubation, showing resilience to prior pH and intestinal component exposure.
- Final bacterial concentration reached 6.62 ± 0.87 log CFU ml(-1) with approximately 6% adhesion.
- No enterotoxin was detected in the ileum, likely due to low bacterial load or Nhe degradation.
Conclusions:
- Mucin retains Bacillus cereus and facilitates its passage into the small intestine.
- Mucin may protect bacterial enterotoxins from degradation by intestinal factors, potentially influencing pathogenesis.
