Supragingival plaque microbiome features in allergic rhinitis and allergic asthma and their association with dental caries: a cross-sectional study

Background Allergic rhinitis (AR) and allergic asthma (AS) are associated with increased risk of dental caries, potentially associated with alterations in the oral microbiome.Objective To characterize supragingival plaque microbiome features and their associations with caries severity in allergic adults.Design This cross-sectional study enrolled patients with cat dander-induced AR or AS, along with age- and sex-comparable normal controls (NC). Supragingival plaque was collected for 16S rRNA gene sequencing. Microbial diversity, ANCOM-BC2 with multiple-testing correction and pseudo-count sensitivity analysis and LEfSe exploratory analysis were performed. Factors of caries severity (DMFT/DMFS) were examined with a random forest model and multivariable negative binomial regression.Results A total of 89 participants (32 AR, 46 AS and 11 NC) were included. Allergic patients exhibited significantly higher α-diversity than NC. ANCOM-BC2 analysis identified 24 taxa with an omnibus FDR threshold; a family-resolved, genus-unclassified Prevotellaceae passed the pseudo-count sensitivity analysis. LEfSe analysis identified Treponema and Bacteroidota as AR-enriched taxa, and Actinobacteriota as AS-enriched taxa. Treponema was the top-ranked random forest feature. Among allergic patients, regular dental check-ups were associated with lower DMFT (IRR = 0.47, 95% CI: 0.30–0.75) and DMFS (IRR = 0.34, 95% CI: 0.17–0.69). Corynebacterium abundance was inversely associated with DMFT (IRR = 0.56, 95% CI: 0.31–0.98), and Actinomyces abundance was positively associated with DMFS (IRR = 2.96, 95% CI: 1.07–8.19).Conclusions Plaque microbial communities differed across groups, and selected taxa were associated with caries severity among allergic adults. Future investigations are needed to evaluate temporality and mechanisms.