Thirty-Day Mortality of Persistent Methicillin-Resistant Bacteremia: Insights from a Retrospective Cohort Study.

Although glycopeptides remain the preferred treatment for methicillin-resistant (MRSA) bacteremia, the treatment of persistent MRSA bacteremia has been challenging. We investigated real-world treatment strategies for persistent MRSA bacteremia, with a specific emphasis on the use of antimicrobial agents and the frequency of changes during the treatment course. We retrospectively identified patients with persistent MRSA bacteremia in four university-affiliated hospitals between 2017 and 2021. The primary objective of this study was to investigate the patterns of antimicrobial uses for MRSA bacteremia. The secondary objectives were evaluating the associated factors with 1) overall 30-day mortality and 2) changing agents during the treatment course. Time-dependent Cox regression analysis was used to adjust for immortal time bias. Among 116 patients, 37.1% underwent antimicrobials switching, primarily prompted by persistent bacteremia. The 30-day mortality rates of groups with and without antimicrobial switching were 21.4% and 44.2%, respectively (=0.010 by log-rank test); however, after adjustment for immortal time bias, there was no statistical significance between the two groups (adjusted hazard ratio 0.24, 95% confidence interval 0.03-2.17, =0.238). Only the Pitt bacteremia score on day 4 and pneumonia were associated with 30-day mortality. Meanwhile, the factors associated with antimicrobial switching were the duration of bacteremia, the initial use of teicoplanin, echocardiogram, and Charlson comorbidity index. This study showed that while over one-third of persistent MRSA bacteremia patients experience changes in antimicrobial agents during treatment, this practice does not significantly improve the 30-day mortality. Our study suggests the need for more effective treatment strategies in managing persistent MRSA bacteremia.