Nosocomial infections due to methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcus: relationships with antibiotic use and cost drivers.

BACKGROUND: Increased incidence of nosocomial infections due to methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) has been associated with the use of certain antibiotics and has resulted in increased morbidity, mortality, and costs of care. OBJECTIVE: To describe relationships between vancomycin and linezolid use and incidence of these nosocomial infections over time and to determine factors associated with the increased costs of care (cost drivers) associated with affected patients. METHODS: The association between institution-wide antibiotic use and the rate of nosocomial MRSA and VRE infections was assessed using segmented regression analysis for interrupted time series. The effect that patient characteristics and procedures, as well as certain antibiotic use, had on costs and length of stay of patients with MRSA or VRE nosocomial infection was also assessed and cost drivers for the 2 types of infections were compared. RESULTS: Our analysis included 206 patients who developed MRSA (n = 187) or VRE (n = 19) nosocomial infection. Although small numbers of VRE nosocomial infection may limit generalizations from our results, we found no significant relationship between vancomycin or linezolid use and the rate of either infection. While mean hospital costs were similar, cost drivers varied somewhat between infection types. CONCLUSIONS: The incidence of MRSA or VRE infections does not appear to be related to the use of vancomycin or linezolid. Costs of care are quite high in some affected patients and, while mean total hospital costs are similar, cost drivers appear to differ between the 2 infection types.