Severity-dependent alterations in oral microbiota and antibiotic resistance in children with dental fluorosis.

BACKGROUD: Dental fluorosis is a prevalent endemic condition, yet its impact on the oral microbiota structure and resistance in children remains understudied. OBJECTIVE: To assess the microbial composition, diversity, functional pathways and co-occurrence patterns among urinary fluoride (UF), bacterial taxa and antibiotic resistance genes in relation to fluorosis severity. Design: Metagenomic analysis of dental plaque was conducted on 96 school-aged children, who were grouped into normal, dubious, very mild, mild, moderate and severe base on fluorosis severity. RESULTS: Microbial diversity increased with fluorosis severity. Actinomyces sp. HMT 175, Actinomyces oris and Corynebacterium matruchotii, Fusobacterium nucleatum and Rothia dentocariosa were significantly enriched in the moderate and severe groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed a reduced relative abundance of genes involved in carbohydrate metabolism and genetic information processing in moderate and severe groups. Network analysis revealed positive correlations among Actinomyces sp. HMT 175, UF levels and GRD33_1 (a carbapenem resistance gene). CONCLUSIONS: These findings highlight severity-dependent shifts in the oral microbiota and resistance, warranting further investigation into fluoride's public health implications.