Ethnicity-specific microbiome in early childhood caries: a functional perspective of oral biofilm.

National surveillance data show persistent racial and ethnic disparities in early childhood caries (ECC), but the underlying causes of these differences have not been determined. This study examined both functional and taxonomic differences in ECC-related microbial activity between two high-risk groups of children: African American (AA) and Latin American Hispanic (LAH). Metatranscriptomic profiling of paired non-caries and caries plaque revealed consistent population-level shifts in gene expression and enabled species-level attribution of metabolically active microbes in caries lesions. A core set of well-established cariogenic organisms was consistently present and highly over-expressed in caries of both groups, including IMPORTANCE: The disparity in tooth decay among young children has long been demonstrated in national surveillance data. While various factors including family, culture, access to health insurance, and medical infrastructure have been studied, the global transcriptomic perspective remains underexplored. Employing RNA-Seq technology, we examine functional and taxonomic differences in caries-associated microbial activity between two high-risk populations. Besides a core set of well-established cariogenic organisms, we observed significant and consistent differences in the active microbial communities between these two high-risk populations, African American (AA) and Latin American Hispanic (LAH) children. In AA children,