Which probiotic strains are cited as examples used to improve oral health by modulating biofilm composition and host responses?

• A. Streptococcus mutans and Actinomyces israelii
• B. Streptococcus salivarius K12 and Lactobacillus reuteri
• C. Porphyromonas gingivalis and Tannerella forsythia
• D. Streptococcus sanguinis and Veillonella atypica

Answer: (B)

Probiotic strategies for oral health focus on shifting the biofilm toward a community that supports health and modulates how the host responds to microbes. Streptococcus salivarius K12 and Lactobacillus reuteri are classic examples because they actively participate in the oral ecosystem rather than just being present. Streptococcus salivarius K12 colonizes the oral mucosa and produces specific bacteriocins that inhibit potential pathogens, helping to shape a less virulent biofilm environment while also influencing local immune signaling. This dual action—reducing harmful colonizers and modulating immune responses—can lower issues like bad breath and opportunistic infections, contributing to a healthier oral microbial balance.

Lactobacillus reuteri also contributes by competing within biofilms and producing antimicrobial compounds such as reuterin, which can suppress cariogenic and other undesirable bacteria. Beyond direct antagonism, L. reuteri can influence host inflammatory responses and salivary factors, supporting a more favorable environment for beneficial microbes. Together, these strains exemplify how probiotics can improve oral health by altering both the biofilm composition and the host’s responses, rather than simply targeting pathogens. In contrast, the other options include known pathogens or strains not typically used as probiotics for oral health, so they don’t fit the concept of probiotic modulation of biofilms and host responses.