Analysis of Antibiotic Transition Patterns in Escherichia coli Bloodstream Infections: A Single-center Retrospective Observational Study

Background : Bloodstream infections are associated with high mortality rates, making appropriate empirical therapy crucial.However, the overuse of broad-spectrum antibiotics contributes to antibiotic resistance.This study focused on Escherichia coli (E.coli) bloodstream infections to assess antibiotic transitions and support effective de-escalation strategies within the Antimicrobial Stewardship Program (ASP) framework. Methods :We conducted a retrospective study involving adult patients with monomicrobial E. coli bloodstream infections at a tertiary hospital between January and June 2025.Clinical and microbiological data were analyzed, and antibiotic transitions were assessed based on susceptibility results within 48 hours of reporting. Results :The study included 46 patients with E. coli bloodstream infections (intervention group, n=21; non-intervention group, n=25).The rate of ESBL (Extended-spectrum β-lactamase)-producing E. coli was significantly higher in the intervention group (61.9% vs. 24.0%,p=0.016).Appropriate antibiotic transitions occurred more frequently in the intervention group (85.7% vs. 40.0%,p=0.002).Although the time to transition was longer in the intervention group (median 13.3 vs. 5.8 days, p=0.204), follow-up blood cultures were performed more often (95.2% vs. 72.0%).No significant difference in 60-day recurrence rates was observed between the two groups. Conclusion :This study examined antibiotic use in E. coli bloodstream infections, finding that interventions