The Oral Cavity, Biofilms and Ventilator-Associated Pneumonia

Abstract

Ventilator-associated pneumonia (VAP) is the most prevalent infection in intensive care units (ICUs) and second only to urinary tract sepsis amongst hospital-acquired infections. The endotracheal tube is an important component in the pathogenesis of VAP, as it both subverts the normal defence mechanisms of the respiratory tract and offers a surface that can support biofilm growth, thereby providing a reservoir of potential respiratory pathogens. Traditionally recognized VAP pathogens include Staphylococcus aureus and Gram-negative bacteria such as Pseudomonas aeruginosa and members of the Enterobacteriaceae family. These microorganisms are not recognized as members of the normal oral microflora, but are thought to infect the lungs endogenously via the oropharyngeal route. Prior to entering the lower respiratory tract, there is evidence that the oral cavity does become colonised by respiratory pathogens. In this regard, it is probable that the normal oral microflora is an influencing factor for VAP, either through affecting recruitment of respiratory pathogens to oral plaque, or to biofilms that develop in the endotracheal tube. Indeed the ability of several Streptococcus species belonging to the normal oral microflora to promote recruitment of bacteria to plaque biofilm through production of extracellular glucans has long been recognised. Recent studies have indeed highlighted that poor oral hygiene is a risk factor for VAP and therefore the maintenance of adequate oral health care in ventilated patients represents an important preventative strategy. Keywords: Biofilm, endotracheal tube, oral hygiene, ventilator-associated pneumonia, intensive care units, hospital-acquired infections, respiratory tract, respiratory pathogens, Staphylococcus aureus, Pseudomonas aeruginosa