Risk Factors for Persistent Methicillin-Resistant Staphylococcus aureus Bacteremia Despite Treatment With Vancomycin

Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia despite treatment with vancomycin is not uncommon. Factors that contribute to vancomycin failure remain poorly understood. A retrospective case-control study was performed to examine factors associated with persistent MRSA bacteremia. All episodes of MRSA bacteremia from 1998 to 2004 were reviewed. Case patients had at least 1 positive blood culture drawn 5 or more days after beginning vancomycin. Two controls for each case were randomly selected with negative blood cultures within 48 hours of starting vancomycin. Of 251 MRSA bloodstream infections, 20 patients met the case definition. The median number of foreign devices, an intravascular device or septic phlebitis as a site of infection, and a maximum vancomycin minimum inhibitory concentration of 2 mu g/mL were significantly associated with persistent bacteremia. In a multivariate model, only the number of foreign devices present at the onset of the bacteremia was found to be an independent predictor.