Evaluating a Program to Reduce MRSA Infections after Cardiothoracic Surgery

Although the incidence of surgical site infections (SSIs) after cardiothoracic (CT) surgery is relatively low, these infections can carry significant morbidity and mortality and can incur substantial costs. The overall incidence of serious deep sternal or mediastinal wound infections ranges from 0.5% to 3%, and Staphylococcus aureus is often linked to half of these infections. Over the past 2 decades, the proportion of SSIs due to methicillinresistant Staphylococcus aureus (MRSA) has been increasing. Because antibiotic therapy for MRSA has been suboptimal, hospitals and other institutions have been attempting to develop strategies aimed at preventing staphylococcal surgical wound infections, especially MRSA, after cardiac surgery. A group of 3 investigators from Rochester General Hospital in Rochester, New York, evaluated and reported on a novel comprehensive MRSA control program [Arch Intern Med. 2011;171(1):68-73] that has resulted in a nearly complete elimination of SSIs caused by MRSA in the 36 months since it was instituted. To evaluate the program, researchers analyzed data from all patients who underwent cardiac surgery and required a median sternotomy incision from January 1, 2004, through January 31, 2010. The intervention program began February 1, 2007. A total of 2766 patients underwent surgery between January 1, 2004, and January 31, 2007 (baseline cohort), and a total of 2496 patients underwent surgery from February 1, 2007, through January 31, 2010 (intervention cohort). An average of 877 CT surgical cases were performed annually from 2004 through January 2010. During the 37-month baseline period, 59 SSIs were identified, for an incidence of 2.1%. Of these, 32 (54%) were attributable to MRSA for an MRSA SSI rate of 1.2%. Before the initiation of the MRSA intervention program, 98 CT surgical staff members, including the unit’s 3 surgeons, were screened for MRSA colonization. Two nurses were positive (2% colonization rate) and were decolonized with a 5-day course of intranasal mupirocin. There was no screening of staff following the institution of the intervention program. After the institution of the program, 56 of the 2496 patients (2.2%) were colonized with MRSA on admission to the CT ward. All but 3 of the colonized patients were negative on subsequent nasal culture before discharge, for an eradication rate of 95%. Most MRSA-colonized patients received intravenous vancomycin in addition to the standard cefazolin prophylaxis, with the exception of several patients who were taken to the operating room emergently and in whom MRSA screening cultures were not available until the following day. According to protocol, all patients, regardless of MRSA colonization status, received intranasal mupirocin for up to 5 days after surgery. After implementation of the MRSA intervention program, 2 of 2496 patients (0.08%) developed an MRSA SSI. This number represents a 93% reduction in MRSA SSIs from the baseline period (32/2766 vs 2/2496; relative risk, 0.069; 95% confidence interval, 0.016-0.286; P<.001). If only patients who completed 6 months of postoperative follow-up are considered, the MRSA SSI rate is similar (2 MRSA infections per 2220 surgical procedures). Overall wound infection rates were also significantly reduced during the intervention period, decreasing from 2.1% to 0.8% (59/2766 vs 20/2496; P<.001). This overall reduction in SSI was primarily attributable to the decrease in MRSA infections, since the decline in other bacterial and yeast infections was not statistically significant. The investigators said the MRSA intervention program has resulted in a near-complete and sustained elimination of MRSA wound infections after cardiac surgery.