Dynamics of oral biofilms associated with mechanical ventilation

Critically ill patients often require mechanical ventilation (MV) to facilitate treatment for respiratory failure or airway protection when consciousness is impaired. Whilst the endotracheal tube (ETT) is an essential interface between the patient and ventilator, it may promote VAP by impeding host defence mechanisms and by translocating microorganisms from dental plaque to the lower airways. Ventilator-associated pneumonia (VAP), which may be challenging to diagnose, is the most frequent hospital-acquired infection in critical care. It has been reported that when patients receive MV the composition of dental plaque changes to include respiratory pathogens such as Meticillin-Resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The primary aim of this research was to confirm that dental plaque communities altered during MV and to identify the potential causes of these changes. A combination of culture-based microbiology, community profiling molecular techniques and proteomic analysis of saliva was performed to analyse the microbiological content of the oral cavity, and to also quantify changes in dental plaque composition and saliva. For the first time, this study comprehensively analysed the dental plaque of mechanically ventilated patients and documented considerable species richness and diversity. Numerous potential respiratory pathogens were detected including Staphylococcus aureus, P. aeruginosa and Streptococcus pneumoniae in approximately one-third of mechanically ventilated patients. In addition, salivary flow rate was decreased and both the salivary pH and concentration of pro-inflammatory cytokines were significantly elevated during intubation. Dental plaque is a reservoir for VAP, and preventing or reducing respiratory colonisation may play a role in the management of ventilated patients. Interventions to prevent colonisation could include the modulation of salivary parameters such as pH and volume and further work may lead to the identification of specific proteins that are significant. Reducing the incidence of VAP will not only reduce mortality in the ICU, but will also have a great impact on hospital economics by reducing inpatient stay