Streptococcus mutans out-competes Streptococcus gordonii in vivo

Area of Science:

• Oral microbiology
• Dental caries research
• Bacterial pathogenesis

Background:

• Streptococcus gordonii and Streptococcus mutans are key colonizers of teeth.
• Specific virulence factors like glucosyltransferases (GtfG, GtfB) and amylase-binding proteins (AbpA/AbpB) influence their colonization.
• Understanding interspecies competition is crucial for managing dental caries.

Purpose of the Study:

• To investigate the competitive interactions between S. gordonii and S. mutans in a rat caries model.
• To determine the impact of diet (non- vs. high-sucrose) and specific gene mutations on colonization and caries induction.
• To assess the potential of S. gordonii as a replacement therapy for caries prevention.

Main Methods:

• Utilized a rat model of human caries with wild-type and mutant strains of S. gordonii and S. mutans.
• Examined colonization dynamics under different dietary conditions (non-sucrose vs. high-sucrose).
• Assessed caries induction based on the abundance of each bacterial species in plaque biofilms.

Main Results:

• S. mutans consistently out-competed S. gordonii in vivo, irrespective of diet, inoculation strategy, or S. gordonii mutations.
• High-sucrose diets exacerbated caries, correlating with S. mutans abundance.
• S. gordonii colonization did not lead to significant caries induction.

Conclusions:

• S. mutans possesses a strong competitive advantage over S. gordonii in the oral environment.
• S. gordonii's inability to outcompete S. mutans makes it an unlikely candidate for caries replacement therapy.
• Findings align with human oral ecology and caries development patterns.