The subgingival microbiota in Down syndrome and non-Down syndrome (non-DS) adults receiving periodic dental care was examined for 40 bacterial species with checkerboard DNA-DNA hybridization, and related to clinical periodontal attachment loss (AL).
A total of 44 Down syndrome, 66 non-DS mentally retarded, and 83 mentally normal adults were clinically evaluated, with subgingival specimens removed and pooled per subject from three interproximal sites on different teeth, and assessed for the presence and levels of 40 bacterial species using species-specific whole genomic DNA probes and checkerboard DNA-DNA hybridization. Significant group differences in species proportions averaged across subjects were evaluated using the Kruskal-Wallis test, and associations between subgingival species and mean subject AL within Down syndrome and non-DS subject groups were quantified with Pearson correlation and multiple linear regression analysis.
Down syndrome subjects exhibited greater AL than non-DS subjects (P = 0.05). Down syndrome subjects yielded most microbial species at levels similar to non-DS subjects, except for higher proportions of Selenomonas noxia, Propionibacterium acnes, Streptococcus gordonii, Streptococcus mitis, and Streptococcus oralis as compared to non-DS study subjects, higher Treponema socranskii than non-DS mentally retarded subjects, and higher Streptococcus constellatus relative to mentally normal subjects. Down syndrome adults classified with periodontitis revealed higher subgingival levels of T. socranskii than non-periodontitis Down syndrome subjects (P = 0.02). Higher subgingival proportions of S. constellatus, Fusobacterium nucleatum subsp. nucleatum, S. noxia and Prevotella nigrescens showed significant positive correlations (r = 0.35 to 0.42), and Actinomyces naeslundii II and Actinomyces odontolyticus negative correlations (r = −0.36 to −0.40), with increasing mean subject AL in Down syndrome adults.
Individuals with DS show higher levels of some subgingival bacterial species and specific associations between certain subgingival bacterial species and loss of periodontal attachment. These findings are consistent with the notion that certain subgingival bacteria may contribute to the increased level of periodontal disease seen in DS individuals, and raise the question as to the reason for increased colonization in DS.