Streptococcus dentisani is a common inhabitant of the oral microbiota worldwide and is found at higher levels in caries-free individuals

Streptococcus dentisani has been proposed as a promising probiotic against tooth decay, due to its ability to buffer acidic pH and to inhibit the growth of oral pathogens. However, it is unknown if this bacterial species has a global distribution. The current study aimed to establish the presence of S. dentisani in oral samples from different geographic locations by identifying the sequence of its 16S rRNA gene in available datasets from across the globe. In addition, an analytical and cross-sectional study was carried out to determine if the levels of this probiotic strain are higher in caries-free individuals compared to those with dental caries. Samples from various geographical sources demonstrated that S. dentisani is present in saliva and dental plaque from individuals of different continents. Typical S. dentisani levels in saliva ranged from 10 4 to 10 5 cells/ml and a total of 10 6 –10 7 cells in dental plaque. Using real-time qPCR, S. dentisani was quantified from supragingival dental plaque of 25 caries-free and 29 caries-active individuals from a Mexican children population, where significantly higher proportions of S. dentisani were found in the caries-free group ( p = 0.002). Finally, a negative correlation was found between caries levels (as measured by the dmft caries index) and the percentage of S. dentisani ( p < 0.001). Thus, the current manuscript indicates that this species has a global distribution, can be found in saliva and dental plaque, and appears to be present in higher numbers in plaque samples from caries-free children.