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

Reduced vancomycin susceptibility (RVS) may lead to poor clinical outcomes in Staphylococcus aureus bacteremia. The objec-tive of this study was to evaluate the clinical and economic impact of RVS in patients with bacteremia due to S. aureus. A cohort study of patients who were hospitalized fromDecember 2007 to May 2009 with S. aureus bacteremia was conducted within a university health system. Multivariable logistic regression and zero-truncated negative binomial regressionmodels were devel-oped 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 to S. aureuswith RVS as defined by a vancomycin Etest MIC of>1.0g/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 associ-ated with increased mortality in patients with S. aureus bacteremia 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-susceptible S. aureus but not methicillin-resistant S. aureus. Further research is needed to identify optimal treatment strategies to reduce mortality associated with RVS in S. aureus bacteremia