Microbial profiling of dental plaque. Microbial profiling of dental plaque from mechanically ventilated patients

Background: Current evidence suggests microorganisms isolated from the oral cavity can initiate ventilator-associated pneumonia (VAP). In critical care medicine, the endotracheal tube (ETT) is a vital medical device that ensures adequate ventilation. Microorganisms isolated from the oral cavity may translocate to the lower airways during mechanical ventilation leading to VAP. Changes within the dental plaque microbiome during mechanical ventilation (MV) have been documented previously, primarily using culture-based techniques. The aim of this study was to use community profiling by high throughput sequencing to comprehensively analyse via community profiling, those microbial changes which have been suggested to occur within dental plaque during MV and following extubation. Methods: 16S rDNA gene sequences were obtained from 38 samples of dental plaque sampled from 13 mechanically ventilated patients and sequenced using the Illumina platform. Sequences were processed using Mothur, applying a 97% gene similarity cut-off for bacterial species level identifications. The results were analysed on the basis of time intervals during mechanical ventilation. Results: A significant ‘microbial shift’ occurred in the microbial community of dental plaque during MV for 8 out of 13 patients. The relative abundance of potential respiratory pathogens (PRP) within the microbiome was shown to increase for the majority of patients during mechanical ventilation. Post-ETT extubation sampling revealed a decrease in the relative abundance of PRP and a compositional change towards a more predominantly (in terms of abundance) oral microbiota including Prevotella spp., lactobacilli and streptococci. Conclusion: Molecular characterisation of the microbiota indicated changes within the plaque to include a higher proportion of putative respiratory pathogens during ventilation. Although these pathogens begin to decrease in abundance once the ETT is removed and the plaque composition returns to that considered more representative of health, they are still detectable and may serve as a reservoir of respiratory pathogens in the longer term. The results highlight the need to better understand the microbial shifts in the oral microbiome in the development of strategies to prevent or reduce VAP and may have implications for the development of other forms of pneumonia such as community acquired infection.