Can clinical and molecular epidemiologic parameters guide empiric treatment with vancomycin for methicillin-resistant Staphylococcus aureus infections?

Reports of vancomycin treatment failure for infections caused by susceptible methicillin-resistant Staphylococcus aureus (MRSA) strains with elevated minimum inhibitory concentration (MIC) has prompted use of high-dose therapy, but nephrotoxicity is a concern. We determined whether clinical and molecular epidemiologic parameters can be used to guide empiric vancomycin therapy and strain susceptibility to alternative agents. Medical charts of 180 hospitalized adults with MRSA infections were reviewed. MICs of vancomycin, daptomycin, linezolid, and tigecycline were determined by Etest. Patient isolates were assayed for genes encoding Panton-Valentine leukocidin (PVL) and SCCmec type. High vancomycin MIC did not correlate with place of acquisition, invasiveness of infection, or history of health care exposure. High MIC was present in 32% of strains overall and in 23% of PVL+, SCCmec IV strains; all were susceptible to alternative agents. Clinicians should not make empiric treatment decisions related to vancomycin use based on history of healthcare exposure risk or residence at onset of infection for patients hospitalized with MRSA infections.