ObjectiveTo determine if head-injured patients with premorbid nasal colonization with Staphylococcus aureus are at increased risk for S. aureus infection.Designor=to9, intensive care unit (ICU) admission, hospitalization in another hospital <24 hrs, no recent use of antibiotics.SettingAcute care trauma facility.PatientsAny patient sustaining acute, blunt, or penetrating injury and meeting the enrollement criteria were eligible.InterventionsSwab cultures of both internal nares were performed within 72 hrs of readmission and cultured for S. Aureus. Patients were prospectively monitored for S. Aureus infections until discharge.Measurements and Main ResultsAdmission nasal cultures were positive (NC+) for S. aureus in 144 of the 776 patients cultured. Forty of the 144 NC+ patients had isolated head (37) or high cervical spine (3) injury, and 11 of that group (27.5%) developed S. aureus infections. The remaining 104 patients positive for S. aureus on admission had no head injury (74) or head combined with torso and extremity injuries (30). S. aureus infection was diagnosed in 11 of the 104 patients (10.6%). The difference in incidence of infections is significant (p < .01), as is the difference in incidence of pneumonia (20% vs. 3.8%, respectively [p < .01]). Organisms causing pneumonia were often the same organisms isolated from the nares on admission.ConclusionsNasal colonization with S. aureus at the time of severe head injury increases the risk of S. aureus pneumonia during hospitalization. Prophylactic measures against S. aureus pneumonia may help reduce the length and cost of hospitalization.(Crit Care Med 1999; 27:798-801)