Intraspecies interactions of Streptococcus mutans impact biofilm architecture and virulence determinants in childhood dental caries

Early childhood dental caries (ECC) is the most common chronic disease among children, especially among low socioeconomic populations. is most frequently associated with initiation of ECC. Although many studies report children with multiple strains (i.e., genotypes) have greater odds of developing ECC, studies investigating intraspecies interactions in dental caries are lacking. This study investigates the impact of intraspecies interactions on cariogenic and fitness traits of clinical isolates using and approaches. Association analysis evaluated if presence of multiple genotypes within the first year of colonization was associated with caries. Initially, clinical isolates from 10 children were evaluated. strains (G09 and G18, most prevalent) isolated from one child were used for subsequent analysis. Biofilm analysis was performed for single and mixed cultures to assess cariogenic traits, including biofilm biomass, intra-polysaccharide, pH, and glucan. Confocal laser scanning microscopy (CLSM) and time-lapse imaging were used to evaluate spatial and temporal biofilm dynamics, respectively. A model was used to assess colonization . Results showed the mean biofilm pH was significantly lower in co-cultured biofilms versus monoculture. Doubling of biofilms was observed by CLSM and colonization in for co-cultured . Individual strains occupied specific domains in co-culture and G09 contributed most to increased co-culture biofilm thickness and colonization in . Biofilm formation and acid production displayed distinct signatures in time-lapsed experiments. This study illuminates that intraspecies interactions of significantly impacts biofilm acidity, architecture, and colonization.IMPORTANCEThis study sheds light on the complex dynamics of a key contributor to early childhood dental caries (ECC) by exploring intraspecies interactions of different strains and their impact on cariogenic traits. Utilizing clinical isolates from children with ECC, the research highlights significant differences in biofilm architecture and acid production in mixed versus single genotype cultures. The findings reveal that co-cultured strains exhibit increased cell density and acidity, with individual strains occupying distinct domains. These insights, enhanced by use of time-lapsed confocal laser scanning microscopy and a model, offer a deeper understanding of ECC pathogenesis and potential avenues for targeted interventions.