Emergency Departments (ED) are usually the first point of contact between patients and hospitals. There is no solid evidence evaluating the activity of antibiotic stewardship programs (ASP) in EDs. We aimed to assess antibiotic prescription appropriateness after the implementation of an ASP in an ED in May 2019 and to determine the risk factors associated with inappropriate antibiotic prescription.

A cross-sectional study was conducted with patients admitted to the ED of the University Hospital Fundación Alcorcón, a second-level university hospital in Spain. All patients admitted to the ED in May 2019, March 2021, and between October and November 2022 were included. We analyzed demographic data, epidemiological variables, comorbidities, empirical antibiotic treatment, previous isolations, and treatment duration. A 30-day follow-up was implemented.

A total of 402 patients were included. No significant improvement in antibiotic appropriateness was observed between the first and second periods (50 % vs. 57.3 %; OR = 1.3, 95 % CI: 0.65–2.76, p = 0.424), while antibiotic appropriateness increased between the first and third periods (50 % vs. 71.2 %; OR = 2.47, 95 % CI: 1.28–4.79, p = 0.007). Factors associated with antibiotic inadequacy were having a urinary catheter (33 % vs. 56 %, p = 0.008, OR: 2.62, 95 % CI: 1.29–5.33), a history of infection/colonization by multidrug-resistant microorganisms (32 % vs. 57 %, p = 0.007), and coming from a retirement home or medium-stay hospital (32 % vs. 47 % vs. 53 %, p = 0.015).The overall use of carbapenems was 9 % (n = 36), showing a decrease in consumption between the first and third periods (26.2 % vs. 7 % vs. 7 %, p < 0.01).