Oral Microbiota of Denture Wearers - Links With Pneumonia?

Objectives: Bacterial pneumonia is a leading cause of morbidity and mortality in the UK elderly population. Reliable assessment of microbial aetiology is highly challenging, delays appropriate treatment and encourages overuse of broad-spectrum antimicrobials, contributing to antimicrobial resistance.
Denture biofilms have been proposed as potential reservoirs of respiratory pathogens, which could promote respiratory infections in susceptible individuals. However, to date no study has characterised the denture-associated microbiota of pneumonia patients.
This research sought to determine whether there was association between the oral microbiota composition, inflammatory mediators and occurrence of pneumonia in denture-wearers.
Methods: Participants were recruited from residential care homes (n=35) and hospital respiratory wards (n=26). Imprint cultures and swabs from the tongue, denture-bearing mucosa and denture-fit surface were used to determine presence of target microbes by culture, and microbiome composition by metataxonomic sequencing. Unstimulated whole saliva was collected for analysis of pro-inflammatory cytokine profiles using cytometric bead arrays.
Results: Importantly, microbial culture revealed presence of the known respiratory pathogens, S. aureus and P. aeruginosa (25% and 11%, respectively), in both groups. However, there was no significant difference in recovery of these species between participant cohorts. Of concern, antimicrobial resistance amongst recovered isolates was high. Metataxonomic analysis similarly showed respiratory pathogen colonisation in participants. Further exploration of compositional shifts in these complex microbial communities and pneumonia development is ongoing. Pro-inflammatory cytokines were detected in saliva, highlighting potential diagnostic value of these samples.
Conclusions: The denture-associated microbiota was found to harbour putative respiratory pathogens, and a reservoir of antimicrobial resistance. Recovery of two targeted species, P. aeruginosa and S. aureus was unrelated to pneumonia status. Ongoing analysis of metataxonomic data supports respiratory pathogen presence and relationships with pneumonia are being assessed. Coupled with detection of salivary inflammatory mediators these techniques offer potential to guide future diagnosis and antimicrobial therapy.