Nasal carriage as a source of Staphylococcus aureus bacteremia.

Background: The consequences of infection with Staphylococcus aureus can be severe, so strategies for prevention are important. We examined S. aureus isolates from blood and from nasal specimens to determine whether the organ isms in the bloodstream originated from the patient's own flora. Methods: In a multicenter study, swabs for culture were obtained from the a nterior nares of 219 patients with S. aureus bacteremia. A total of 723 iso lates were collected and genotyped. In a second study, 1640 S. aureus isola tes from nasal swabs from 1278 patients were collected over a period of fiv e years and then compared with isolates from the blood of patients who subs equently had S. aureus bacteremia. Results: In the multicenter study of S. aureus bacteremia, the blood isolat es were identical to those from the anterior nares in 180 of 219 patients ( 82.2 percent). In the second study, 14 of 1278 patients who had nasal colon ization with S. aureus subsequently had S. aureus bacteremia. In 12 of thes e 14 patients (86 percent), the isolates obtained from the nares were clona lly identical to the isolates obtained from blood 1 day to 14 months later. Conclusions: A substantial proportion of cases of S. aureus bacteremia appe ar to be of endogenous origin since they originate from colonies in the nas al mucosa. These results provide support for strategies to prevent systemic S. aureus infections by eliminating nasal carriage of S. aureus. (N Engl J Med 2001;344:11-6.) Copyright (C) 2001 Massachusetts Medical Society.