Staphylococcus aureus Infections After Elective Cardiothoracic Surgery: Observations From an International Randomized Placebo-Controlled Trial of an Investigational S aureus Vaccine

Abstract

Abstract Background.  An unmet need to prevent Staphylococcus aureus (SA) infections after cardiothoracic surgery persists despite current practices. Cost-effective implementation of preventive strategies requires contemporary knowledge about modifiable risk factors. Methods.  From 2007 to 2011, an international, double-blind, randomized placebo-controlled trial of a novel SA vaccine (V710) was conducted in 7664 adults scheduled for median sternotomy at 164 sites. We analyzed SA infections developing up to 360 days postoperatively in 3832 placebo recipients. Results.  Coronary artery bypass grafting was performed in 80.8% (3096 of 3832) of placebo recipients. The overall incidence of any postoperative SA infection was 3.1% (120 of 3832). Invasive SA infections (including bacteremia and deep sternal-wound infections) developed in 1.0%. Methicillin-resistant SA (MRSA) accounted for 19% (23 of 120) of SA infections, with 57% (13 of 23) of the MRSA infections occurring in diabetic patients. All-cause mortality was 4.1% (153 of 3712) in patients without SA infection, 7.2% (7 of 97) in methicillin-susceptible SA (MSSA) infections, and 17.3% (4 of 23) in MRSA infections (P < .01). Staphylococcus aureus nasal carriage was detected preoperatively in 18.3% (701 of 3096) patients, including 1.6% colonized with MRSA. Postoperative SA infections occurred in 7.0% (49 of 701) of colonized patients versus 2.3% (71 of 3131) of patients without colonization (relative risk = 3.1 [95% confidence interval, 2.2–4.4]). Conclusions.  In this large international cohort of patients undergoing cardiac surgery and observed prospectively, invasive postoperative SA infections occurred in 1% of adult patients despite modern perioperative management. The attributable mortality rates were 3% for MSSA and 13% for MRSA infections. Preoperative nasal colonization with SA increased the risk of postoperative infection threefold. The utility of strategies to reduce this incidence warrants continued investigation.