Is the burden of Staphylococcus aureus among patients with surgical-site infections growing?

Surgical-site infections (SSIs) are an important cause of illness and death among individuals receiving healthcare.1 Staphylococcus aureus has consistently been reported as the most frequent cause of infections at surgical sites, and, because it is more virulent than other frequent causes, accounts for a large proportion of the morbidity and mortality associated with these infections.2,3 In this issue of Infection Control and Hospital Epidemiology, a series of articles address various issues regarding SSIs and their etiology.4-8 A consistent theme among these articles is the gravity and frequency of S. aureus as a cause of infections in surgical patients, and the findings suggest that the proportion and clinical impact of SSIs caused by S. aureus may be increasing. In the first article addressing this subject, McGarry et al.4 examine the impact of S. aureus SSI on clinical and fiscal outcomes among elderly patients. In this nested cohort study, elderly patients (70 years or older) with S. aureus SSI were compared with elderly surgical patients who did not develop infection, as well as with a group of younger patients (18 to 60 years old) with SSI due to S. aureus. When compared with uninfected patients of similar age and with similar underlying illnesses, elderly patients with S. aureus SSI had a higher mortality rate, longer hospitalization, and increased hospital charges. In addition, when older patients were compared with younger patients with S. aureus SSI in multivariate analyses controlling for comorbid illnesses, procedure type, and other factors, the investigators found that being 70 years of age or older was an independent predictor of death (adjusted odds ratio, 2.9; 95% confidence interval, 1.1 to 7.6), longer hospital stay (13 vs 9 days; P = .001), and increased hospital charges ($45,767 vs $85,648; P < .001). These data suggest that the clinical impact of S. aureus SSI may be more severe among elderly patients when compared with younger patients who have similar infections. Although these findings may not be unexpected, they do carry particular significance considering the changing demographic of the U.S. population. Increasing life expectancy and the aging of the “baby boomer” generation are expected to contribute to a dramatic increase in the number of older individuals living in this country during the next two decades. U.S. Census Bureau projections forecast that between 2000 and 2020 there will be a 56% increase in the number of individuals 65 years of age and older.9 As a result, larger numbers of elderly patients will require surgery in the coming years. In one projection, cardiothoracic and orthopedic surgical work is expected to grow by 42% and 28%, respectively, between 2001 and 2020.10 If S. aureus SSI rates remain constant, then the number of S. aureus SSIs among the elderly, a particularly vulnerable group as suggested by the article from McGarry et al.,4 will increase substantially. Three additional articles published in this issue of Infection Control and Hospital Epidemiology5-7 suggest that S. aureus may be playing an increasingly prominent etiologic role in SSI associated with coronary artery bypass graft (CABG) procedures and joint replacement surgery, procedures that are performed primarily in elderly patient populations. In a review of 3,443 CABG procedures performed in a Detroit hospital, Sharma et al.5 report that sternal SSI developed in 122 (3.5%). S. aureus was the most frequently isolated pathogen, accounting for 46 (49%) of the SSIs in which a single pathogen was isolated. Of the 55 infections caused by S. aureus, 20 (36%) were caused by