In Vivo Colonization with Candidate Oral Probiotics Attenuates Colonization and Virulence of Streptococcus mutans

A collection of 113 strains from supragingival dental plaque of caries-free individuals were recently tested for direct antagonism of the dental caries pathogen , and for their capacity for arginine catabolism via the arginine deiminase system (ADS). To advance their evaluation as potential probiotics, twelve strains of commensal oral streptococci with various antagonistic and ADS potentials were assessed in a mouse model for oral (i.e., oral mucosal pellicles and saliva) and dental colonization under four diets (healthy or high-sucrose, with or without prebiotic arginine). Colonization by autochthonous bacteria was also monitored. One strain failed to colonize, whereas oral colonization by the other eleven strains varied by 3 log units. Dental colonization was high for five strains regardless of diet, six strains increased colonization with at least one high-sucrose diet, and added dietary arginine decreased dental colonization of two strains. sp. A12 (high ADS activity and antagonism) and two engineered mutants lacking the ADS (Δ ) or pyruvate oxidase-mediated H O production (Δ ) were tested for competition against UA159. A12 wild type and Δ colonized only transiently, whereas Δ persisted, but without altering oral or dental colonization by In testing four additional candidates, BCC23 markedly attenuated oral and dental colonization, enhanced colonization of autochthonous bacteria, and decreased severity of smooth surface caries under highly cariogenic conditions. Results demonstrate the utility of the mouse model to evaluate potential probiotics, revealing little correlation between antagonism and competitiveness against Our results demonstrate testing of potential oral probiotics can be accomplished and can yield information to facilitate the ultimate design and optimization of novel anti-caries probiotics. We show human oral commensals associated with dental health are an important source of potential probiotics that may be used to colonize patients under dietary conditions of highly varying cariogenicity. Assessment of competitiveness against dental caries pathogen and impact on caries identified strains or genetic elements for further study. Results also uncovered strains that enhanced oral and dental colonization by autochthonous bacteria when challenged with , suggesting cooperative interactions for future elucidation. Distinguishing a rare strain that effectively compete with under conditions that promote caries further validates our systematic a