Testing of candidate probiotics to prevent dental caries induced by Streptococcus mutans in a mouse model

We evaluated two species of human oral commensal streptococci in protection against dental caries induced by Streptococcus mutans.Candidate probiotics, Streptococcus sp. A12, Streptococcus sanguinis BCC23 and an arginine deiminase mutant of BCC23 (∆arcADS) were tested for their ability to reduce S. mutans-induced caries in an established mouse model. Mice were colonized with a probiotic, challenged with S. mutans, then intermittently reinoculated with a probiotic strain. Oral colonization of each strain and autochthonous bacteria was assessed by quantitative polymerase chain reaction. Both BCC23 strains, but not A12, were associated with markedly reduced sulcal caries, persistently colonized mucosal and dental biofilms, and significantly lowered S. mutans counts. All three strains enhanced mucosal colonization of autochthonous bacteria. In a follow-up experiment, when S. mutans was established first, dental and mucosal colonization of S. mutans was unaltered by a subsequent challenge with either BCC23 strain. Results between BCC23 and BCC23 ∆arcADS were equivalent.BCC23 is a potential probiotic to treat patients at high caries risk. Its effectiveness is independent of ADS activity, but initial dental cleaning to enhance establishment in dental biofilms may be required.In vivo testing of candidate probiotics is highly informative, as effectiveness is not always reflected by genotype or in vitro behaviours.