December 15, 2008
Every day in emergency rooms across America, hospital staff must insert plastic ventilation tubes into the airways of their sick or severely injured patients to keep them breathing. Unfortunately for those who have the tubes in place for 48 hours or longer, at least one in 10 will develop a bacterial infection in their lungs. In some cases, the resulting pneumonia will prove fatal. In others, the infection – known as ventilator-associated pneumonia, or VAP - will prolong the patient’s hospital stay from two weeks to a month on average, often resulting in extra hospital fees of $40,000 or more.
Where do the bacteria come from? One strong possibility is the mouth. Studies suggest that opportunistic respiratory pathogens first colonize the teeth and then migrate into the lower airway, colonize the ventilator tubes, and infect the lungs. Now, in the December 15 issue of the journal Clinical Infectious Diseases, NIDCR grantees add compelling evidence to support the oral bacteria-VAP link. In a clinical study of 100 hospital trauma patients who received mechanical ventilation, the scientists collected dental plaque and tracheal secretions on the day of admission and every 48 hours thereafter. They then cultured each sample to isolate a predetermined array of respiratory pathogens. The scientists detected their pathogens of interest in the mouths of 60 patients. Of these individuals, 30 were selected for detailed molecular analyses because their mouths, tracheas, and lungs were all colonized by more than one of the pathogens. The scientists ultimately found that the oral isolates of Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter species, and other pathogenic species were genetically indistinguishable from the same species present in the lungs. In fact, almost half of the Pseudomonas strains had identical genetic profiles between patients, suggesting a common environmental source of infection.