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Feeding by mucin and intestinal growth of some enteric bacterial pathogens
1Institute of Microbiology, University Medical School, Pécs.
Abstract:
Enteroinvasive Escherichia coli, Salmonella typhi-murium, Shigella sonnei, Shigella flexneri, as well as E. coli K-12 show dose dependent growth in minimal medium completed with purified hog gastric "Granular Mucin". This ability is based on alpha-galactosidase production: defective, melibiose (and galactose) non-fermenting K-12 mutant were unable to utilize mucin. The viability of the parent K-12 strain in the cecal content of mice is significantly higher than that of its Mel- mutant phenotype. In mixed infections of mice the parent strain was the only one to be able to establish a monoflora against its Mel- or Gal- mutants. Among other mechanisms, the growing ability in the intestinal mucous layer may be an additional virulence factor when the enteric pathogens are exposed to a competitive antagonism of the normal flora.
Insights
Certain enteric pathogens, including Escherichia coli and Salmonella, can grow on intestinal mucin due to alpha-galactosidase production. This mucin utilization is a key factor for pathogen survival and colonization in the gut.
Area of Science:
- Microbiology
- Gastroenterology
- Pathogen Virulence
Background:
- Enteric pathogens face competition from the normal gut flora.
- Mucin, a major component of the intestinal mucous layer, presents a potential nutrient source.
- The ability to utilize host-derived substrates can be a significant factor in pathogen colonization.
Purpose of the Study:
- To investigate the role of mucin utilization in the growth and colonization of enteric pathogens.
- To determine the enzymatic basis for mucin utilization by specific bacterial strains.
- To assess the contribution of mucin utilization to pathogen virulence in a host model.
Main Methods:
- Growth assays of various enteric bacteria (e.g., Escherichia coli, Salmonella typhi-murium, Shigella) in minimal medium supplemented with hog gastric mucin.
- Characterization of bacterial mutants defective in melibiose and galactose fermentation (alpha-galactosidase activity).
- In vivo competition experiments using parent strains and their respective mutants in a mouse cecal colonization model.
Main Results:
- Enteroinvasive E. coli, S. typhi-murium, Shigella, and E. coli K-12 demonstrated dose-dependent growth on purified hog gastric mucin.
- M UCL utilization was dependent on alpha-galactosidase activity; melibiose-negative mutants could not utilize mucin.
- The parent E. coli K-12 strain showed significantly higher viability and colonization success in mouse cecal content compared to its melibiose-negative mutant.
- In mixed infections, the parent strain outcompeted its mutants, establishing a monoflora.
Conclusions:
- Alpha-galactosidase production enables enteric pathogens to utilize intestinal mucin for growth.
- The ability to grow on mucin is a significant virulence factor, aiding pathogens in overcoming competitive antagonism from the normal gut flora.
- Targeting mucin utilization pathways could be a potential strategy to control enteric pathogen infections.