Incidence of and preoperative risk factors for Staphylococcus aureus bacteremia and chest wound infection after cardiac surgery

OBJECTIVE. Staphylococcus aureus infections after cardiac surgery result in significant morbidity and mortality. Identifying patients at elevated risk for these infections preoperatively could facilitate efforts to reduce infection rates. The objectives of this study were to estimate the incidence of postoperative S. aureus infections in cardiac surgery patients, to identify preoperative risk factors for these infections, and to establish a patient risk profile by means of data available to clinicians prior to surgery. DESIGN. Cohort study. SETTING. Eight medical centers that participate in the Society of Thoracic Surgeons National Cardiac Database. PATIENTS. Patients who were undergoing elective cardiac surgery during the period January 1, 2000 through December 31, 2004. METHODS. Clinical and microbiological data from 16,386 patients were combined. Multivariable stepwise logistic regression analysis was performed to predict S. aureus infection, which was defined by culture results. RESULTS. Of the 16,386 patients, 205 (1.3%) developed S. aureus bloodstream or chest wound infection within 90 days after surgery. On multivariable analysis, bootstrap-validated preoperative risk factors for S. aureus bloodstream or chest wound infection included a body mass index greater than 40 (adjusted odds ratio [aOR], 1.9 [95% confidence interval {CI}, 1.1-3.2]), chronic renal failure (aOR, 1.8 [95% CI, 1.1-2.9]), and chronic lung disease (aOR, 1.4 [95% CI, 1.0-2.0]). Only 8 patients had all 3 risk factors. CONCLUSIONS. Although preoperative risk factors can be easily identified, the majority of patients who developed S. aureus infections after cardiac surgery did not have any risk factors. Preventive measures should not be restricted to a select group of cardiac surgery patients and should rather address the entire patient population.