Dietary Nitrite Drives Disease Outcomes in Oral Polymicrobial Infections.

Area of Science:

• Oral microbiology
• Dental caries research
• Antimicrobial strategies

Background:

• Streptococcus mutans is a primary cause of dental caries, thriving in oral biofilms.
• High salivary nitrite levels correlate with lower caries prevalence.
• Nitrite combined with hydrogen peroxide-producing bacteria generates antimicrobial reactive nitrogen species.

Purpose of the Study:

• To investigate the effect of nitrite on S. mutans virulence during polymicrobial infections with Streptococcus parasanguinis.
• To determine if nitrite can inhibit S. mutans growth, biofilm formation, and glucan production in vitro.
• To evaluate the in vivo efficacy of S. parasanguinis and nitrite in preventing dental caries.

Main Methods:

• In vitro studies of dual-species biofilms (S. mutans and S. parasanguinis) with and without nitrite.
• Assessment of S. mutans growth, biofilm formation, and glucan production.
• In vivo rat model of dental caries, comparing single S. mutans infection with co-colonization and nitrite treatment.

Main Results:

• The combination of S. parasanguinis and nitrite inhibited S. mutans growth and biofilm formation in vitro.
• Glucan production by S. mutans was significantly reduced in the presence of S. parasanguinis and nitrite.
• In vivo, rats treated with S. parasanguinis and nitrite showed significantly reduced enamel and dentin carious lesions.

Conclusions:

• Commensal streptococci, particularly S. parasanguinis, combined with nitrite, offer protection against S. mutans pathogenesis.
• Nitrite modulates the oral microbiome, inhibiting a key cariogenic bacterium.
• Modulating oral nitrite concentrations presents a promising strategy for combating dental caries.