Clinical impact of methicillin-resistant Staphylococcus aureus bacteremia based on propensity scores

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen not only in nosocomial infections, but also in community-associated infections. The aim of this study was to evaluate the impacts of methicillin resistance on mortality, length of hospitalization, and hospital costs via propensity score matching in S. aureus bacteremia. A propensity-matched case-control study was conducted in a tertiary hospital in Korea from 2003 to 2008. A total of 266 patients who had clinically significant S. aureus bloodstream infections were investigated. Fifty-three propensity-matched case-control pairs with MRSA bacteremia were likely to have stayed in the hospital longer before developing bacteremia (mean 25.0 vs. 6.1 days; P = 0.01). However, after developing bacteremia, the differences in the mean duration of hospital stay was not significant (mean 35.0 vs. 28.7 days; P = 0.33). Similar numbers of MRSA and methicillin-susceptible S. aureus (MSSA) patients died (P = 0.48). The mean total hospital costs after S. aureus bacteremia increased more for MRSA patients compared to MSSA patients. However, this difference was not statistically significant ($9,369.6 vs. $8,355.8; P = 0.62). This study indicates that MRSA bacteremia is not associated with higher risks of mortality or hospital costs. It is, however, associated with a substantial increase in the length of hospital stay as compared to MSSA bacteremia. This information may help clinicians and policymakers derive methods to control the impacts of MRSA infection.