Salivary changes in mechanically ventilated patients are associated with respiratory pathogen colonization of dental plaque

Objectives: Ventilator associated pneumonia (VAP) is an infection of mechanically ventilated (MV) patients with high morbidity and mortality. Importantly, VAP has been linked to changes in the oral microbiome where dental plaque becomes colonized with respiratory pathogens during mechanical ventilation. The cause(s) of this microbial change has not been determined, and this is important since the prevention of dental plaque providing a reservoir of VAP pathogens would be a key management tool. The objectives of this study were to analyse salivary parameters in MV patients and relate any changes to the dynamics of plaque microbial composition.
Methods: Dental plaque and saliva samples were obtained from 107 MV patients during mechanical ventilation and post extubation, using paper points and Salivette devices, respectively. The microbial composition of plaque was established by culture and next generation sequencing, whilst volume, pH and total protein concentration of saliva was also measured. Protein composition of saliva was also determined using gel-based and LC-MALDI methodology. Inflammatory cytokines in saliva, including TNFα, IL-1β, IL-6, IL-8 and IL-1β were also determined using cytometric beads array (CBA).
Results: A ‘microbial shift’ in the dental plaque of MV patients was established with colonization by respiratory pathogens occurring during MV. Importantly, a reversion of this change to a dental plaque associated with health was encountered following extubation. During MV associated changes in saliva included a reduced volume and pH, together with changes in the salivary proteome. Significant increases in the pro-inflammatory cytokines IL-6, IL-1β and IL-8 were also evident during MV, and these reduced to levels observed in healthy volunteers post extubation.
Conclusions: Observed changes in salivary factors in MV patients may be lead to an oral environment conducive to the colonization of respiratory pathogens in dental plaque, recognized as a risk factor for VAP. These results can be exploited for the management of MV patients. Administration of an appropriate artificial saliva of protein content and pH could limit respiratory pathogen colonization of plaque, whilst monitoring salivary cytokine profiles may serve as a non-invasive diagnostic/prognostic marker for VAP in MV patients.