Inappropriate therapy for methicillin-resistant Staphylococcus aureus: Resource utilization and cost implications*

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Abstract
Background: Methicillin-resistant Staphylococcus aureus causes significant morbidity and mortality. Initially inappropriate antibiotic therapy for methicillin-resistant S. aureus increases the risk for mortality. The impact of initially inappropriate antibiotic therapy on hospital length of stay and costs remains unknown. Methods: We identified patients admitted with nonnosocomial methicillin-resistant S. aureus sterile-site infections during a 3 yr period and compared those given appropriate antibiotic therapy with those given initially inappropriate antibiotic therapy. Appropriate therapy was defined based on timely administration of an anti-infective to which the pathogen was in vitro susceptible. Hospital length of stay served as the primary end point whereas total hospital costs represented a secondary end point. We attempted to adjust for multiple potential confounders including demographics, comorbid illnesses, infection characteristics, and severity of illness. We conducted subgroup analyses in patients who survived their hospital stay and in those requiring admission to the intensive care unit. Results: The cohort included 291 patients and 77% received initially inappropriate antibiotic therapy. Approximately one in five patients died during their hospitalization. The median length of stay among the appropriately treated population was 2 days shorter than those given initially inappropriate antibiotic therapy (7.1 vs. 9.3 days, p = .050). After adjusting for covariates in a Cox proportional hazards model, initially appropriate therapy remained associated with a reduced length of stay (hazard ratio: 0.69, 95% confidence interval: 0.51–0.92, p = .013). Median crude costs in those treated appropriately were $13,688 compared with $19,427 (p = .019). Restricting the analysis to either hospital survivors or to those needing intensive care did not alter our observations. Conclusion: Initially inappropriate antibiotic therapy for methicillin-resistant S. aureus prolongs length of stay and increases hospital costs. Efforts to lower rates of initially inappropriate antibiotic therapy for methicillin-resistant S. aureus sterile-site infections will likely improve outcomes for both patients and for healthcare institutions.