Compositional shifts within the denture- associated bacteriome in pneumonia-an analytical cross- sectional study

Introduction. Bacterial pneumonia is a common cause of morbidity and mortality in elderly individuals. While the incidence of edentulism is falling, approximately 19 % of the UK population wear a full or partial removable denture. Despite advances in denture biomaterials, the majority of dentures are fabricated using polymethyl-methacrylate. Growing evidence suggests that colonization of the oral cavity by putative respiratory pathogens predisposes individuals to respiratory infection, by transloca-tion of these microorganisms along the respiratory tract. Hypothesis/Gap Statement. We hypothesized that denture surfaces provide a susceptible colonization site for putative respira-tory pathogens, and thus could increase pneumonia risk in susceptible individuals. Aim. This study aimed to characterize the bacterial community composition of denture-wearers in respiratory health compared with individuals with a confirmed diagnosis of pneumonia. Methodology. This was an analytical cross-sectional study, comparing frail elderly individuals without respiratory infection (n=35) to hospitalized patients with pneumonia (n=26). The primary outcome was the relative abundance of putative respira-tory pathogens identified by 16S rRNA metataxonomic sequencing, with quantitative PCR used to identified Streptococcus pneumoniae. Results. There was a statistically significant increase in the overall relative abundance of putative respiratory pathogens (P<0.0001), with a greater than 20 -fold increase in the bioburden of these microorganisms. In keeping with these findings, there were significant shifts in bacterial community diversity (Chao index, P=0.0003) and richness (Inverse Simpson index P<0.0001) in the denture-associated microbiota of pneumonia patients compared with control subjects. Conclusion. Within the limitations of this study, our evidence supports the role of denture acrylic biomaterials as a potential colonization site for putative respiratory pathogens, which may lead to an increased risk of pneumonia in susceptible individu-als. These findings support prior observational studies which have found denture-wearers to be at increased risk of respiratory infection. Further research is needed to confirm the sequence of colonization and translocation to examine potential causal relationships.