Physiologic factors contributing to a transition in oral immunity among mechanically ventilated adults

Ventilator-associated pneumonia (VAP), a specific type of nosocomial pneumonia, occurs in approximately 21% of patients in intensive care, and the mortality can be as high as 71%. VAP causes considerable mortality and morbidity, and it exponentially increases health care costs. The incidence of VAP is associated with oropharyngeal colonization of gram-negative bacteria. Within 48 h of hospital admission, the composition of the oropharyngeal flora of critically ill patients undergoes a change from the usual gram-positive streptococci and dental pathogens to a predominant gram-negative flora that includes more virulent organisms, which predispose patients to VAP. Identification and understanding of this oral transition from gram-positive to predominantly gram-negative flora may assist health care professionals in differentiating among oral immune markers that suggest compromised immunity. The purpose of this article is to provide a review of the literature that promotes an understanding of current knowledge about the transition of oral immunity in mechanically ventilated patients.