Modification of reported antibiotic susceptibility testing according to the EUCAST recommendations: Evaluation of the appropriateness of antibiotic prescriptions in a university hospital.

Objectives: In January 2022, EUCAST guidelines recommending replacement of the "intermediate" category with a "susceptible, increased exposure" (SFP) category were implemented in our hospital. We aimed to assess the impact of these changes on antibiotic prescriptions for Pseudomonas aeruginosa and Staphylococcus aureus infections.

Methods: This retrospective before-after study included adult inpatients with monobacterial infections between March-August 2021 (BEFORE) and March-August 2022 (AFTER). Antibiotic use and relevance were compared. Meropenem was masked when imipenem was categorized as SFP.

Results: We included 240 antibiotic susceptibility tests (195 patients). Infectious disease consultations increased significantly during implementation (53.0 % vs. 28.9 %, p = 0.0005). Meropenem prescriptions for P. aeruginosa declined (13.8 %-6.2 %), while high-dose regimens for SFP antibiotics likewise decreased (50.0 %-35.4 %). Overall, prescription appropriateness remained high (>92 %).

Conclusion: The introduction of SFP reporting was associated with increased ID consultation and a trend toward reduced broad-spectrum use, highlighting a need for targeted prescriber education.