Postoperative <i>Staphylococcus aureus</i> Infections in Medicare Beneficiaries

<div><p><i>Staphylococcus aureus (S. aureus)</i> infections are important because of their increasing frequency, resistance to antibiotics, and high associated rates of disabilities and deaths. We examined the incidence and correlates of <i>S. aureus</i> infections following 219,958 major surgical procedures in a 5% random sample of fee-for-service Medicare beneficiaries from 2004–2007. Of these surgical patients, 0.3% had <i>S. aureus</i> infections during the hospitalizations when index surgical procedures were performed; and 1.7% and 2.3%, respectively, were hospitalized with infections within 60 days or 180 days following admissions for index surgeries. <i>S. aureus</i> infections occurred within 180 days in 1.9% of patients following coronary artery bypass graft surgery, 2.3% following hip surgery, and 5.9% following gastric or esophageal surgery. Of patients first hospitalized with any major infection reported during the first 180 days after index surgery, 15% of infections were due to <i>S. aureus</i>, 18% to other documented organisms, and no specific organism was reported on claim forms in 67%. Patient-level predictors of <i>S. aureus</i> infections included transfer from skilled nursing facilities or chronic hospitals and comorbid conditions (e.g., diabetes, congestive heart failure, chronic obstructive pulmonary disease, and chronic renal disease). In a logarithmic regression, elective index admissions with <i>S. aureus</i> infection stayed 130% longer than comparable patients without that infection. Within 180 days of the index surgery, 23.9% of patients with <i>S. aureus</i> infection and 10.6% of patients without this infection had died. In a multivariate logistic regression of death within 180 days of admission for the index surgery with adjustment for demographics, co-morbidities, and other risks, <i>S. aureus</i> was associated with a 42% excess risk of death. Due to incomplete documentation of organisms in Medicare claims, these statistics may underestimate the magnitude of <i>S. aureus</i> infection. Nevertheless, this study generated a higher rate of <i>S. aureus</i> infections than previous studies.</p>