Preoperative risk factors for nasal carriage of Staphylococcus aureus.

Staphylococcus aureus nasal carriage is a risk factor for surgical-site infections (SSIs) caused by S. aureus, and eradication of carriage reduces postoperative nosocomial infections caused by it. No study has compared large groups of preoperative carriers and non-carriers to identify factors that are linked to S. aureus nasal carriage. While conducting a clinical trial evaluating whether mupirocin prevented S. aureus SSIs, we prospectively collected data on 70 patient characteristics that might be associated with S. aureus carriage. We performed stepwise logistic regression analysis. Of the 4,030 patients, 891 (22%) carried S. aureus. Independent risk factors for S. aureus nasal carriage were obesity (odds ratio [OR], 1.29; 95% confidence interval [CI95], 1.11-1.50), male gender (OR, 1.29; CI95, 1.11-1.51), and a history of a cerebrovascular accident (OR, 1.53; CI95, 1.03-2.25) for all patients. Factors associated with nasal carriage varied somewhat by surgical specialty. In all groups, preoperative use of antimicrobial agents was independently associated with a lower risk of carrying S. aureus in the nares. Previously identified risk factors were not significantly associated with S. aureus nasal carriage in this large group of surgical patients. Male gender, obesity, and a history of a cerebrovascular accident were identified as risk factors for S. aureus nasal carriage. It remains to be seen whether preoperative weight loss would reduce the rate of nasal carriage. In addition, the value of screening this patient population for S. aureus nasal carriage merits further investigation.