Effect of Reduced Vancomycin Susceptibility on Clinical and Economic Outcomes in Staphylococcus aureus Bacteremia

Abstract

ABSTRACTReduced vancomycin susceptibility (RVS) may lead to poor clinical outcomes inStaphylococcus aureusbacteremia. The objective of this study was to evaluate the clinical and economic impact of RVS in patients with bacteremia due toS. aureus. A cohort study of patients who were hospitalized from December 2007 to May 2009 withS. aureusbacteremia was conducted within a university health system. Multivariable logistic regression and zero-truncated negative binomial regression models were developed to evaluate the association of RVS with 30-day in-hospital mortality, length of stay, and hospital charges. One hundred thirty-four (34.2%) of a total of 392 patients had bacteremia due toS. aureuswith RVS as defined by a vancomycin Etest MIC of >1.0 μg/ml. Adjusted risk factors for 30-day in-hospital mortality included the all patient refined-diagnosis related group (APRDRG) risk-of-mortality score (odds ratio [OR], 7.11; 95% confidence interval [CI], 3.04 to 16.6), neutropenia (OR, 13.4; 95% CI, 2.46 to 73.1), white blood cell count (OR, 1.05; 95% CI, 1.01 to 1.09), immunosuppression (OR, 6.31; 95% CI, 1.74 to 22.9), and intensive care unit location (OR, 3.51; 95% CI, 1.65 to 7.49). In multivariable analyses, RVS was significantly associated with increased mortality in patients withS. aureusbacteremia as a result of methicillin-susceptible (OR, 3.90; 95% CI, 1.07 to 14.2) but not methicillin-resistant (OR, 0.53; 95% CI, 0.19 to 1.46) isolates. RVS was associated with greater 30-day in-hospital mortality in patients with bacteremia due to methicillin-susceptibleS. aureusbut not methicillin-resistantS. aureus. Further research is needed to identify optimal treatment strategies to reduce mortality associated with RVS inS. aureusbacteremia.