In vitro evaluation of nutrients that selectively confer a competitive advantage to lactobacilli

Area of Science:

• Microbiology
• Nutritional Science
• Infectious Disease

Background:

• Lactobacillus acidophilus is a beneficial bacterium found in the human gut and urogenital tract.
• Escherichia coli is a common pathogen that can cause infections, including those in the female urogenital tract.
• Prebiotics are non-digestible food ingredients that selectively stimulate the growth and/or activity of beneficial bacteria.

Purpose of the Study:

• To develop and utilize an in vitro assay to assess the competitive interaction between Lactobacillus acidophilus and Escherichia coli.
• To investigate the effect of fructo-oligosaccharide on the ability of L. acidophilus to outcompete E. coli.
• To validate the findings using a skin simulant model mimicking the vulvar environment.

Main Methods:

• A co-culture assay was developed to test the competitive ability of L. acidophilus against E. coli in the presence of various nutrients.
• Growth curves were generated for E. coli in single culture to assess the direct effect of fructo-oligosaccharide.
• A skin simulant model was employed to validate the in vitro findings under conditions mimicking the vulvar environment.

Main Results:

• In mixed cultures, the addition of fructo-oligosaccharide significantly enhanced the ability of L. acidophilus to outcompete E. coli.
• In the absence of fructo-oligosaccharide, E. coli showed a competitive advantage over L. acidophilus.
• Fructo-oligosaccharide did not directly inhibit or promote the growth of E. coli in single cultures, indicating an indirect competitive mechanism.
• The competitive advantage conferred by fructo-oligosaccharide to L. acidophilus was confirmed in the skin simulant model.

Conclusions:

• Fructo-oligosaccharides can promote the competitive exclusion of pathogenic E. coli by beneficial L. acidophilus.
• The co-culture assay serves as an effective in vitro screening tool for identifying nutrients that support beneficial urogenital flora.
• These findings suggest a potential strategy for managing or preventing urogenital infections by modulating the microbiome with prebiotics.