Effect of a multimodal intervention in general and digestive surgery wards on carbapenem use and antimicrobial resistance: protocol for a prospective, quasi-experimental interrupted time-series study.

INTRODUCTION: Infections are particularly common among hospitalised patients in surgical wards. Carbapenem antibiotics, major drivers of antimicrobial resistance, are frequently prescribed in this setting, often inappropriately and for unnecessarily prolonged durations. International guidelines emphasise the need for comprehensive multimodal antimicrobial stewardship programmes to optimise antibiotic use; however, evidence supporting their routine application in surgical wards remains scarce and is mostly derived from retrospective analyses or single-component interventions. This study aims to evaluate the impact of an integrated, multimodal antimicrobial stewardship intervention on carbapenem consumption, antimicrobial resistance patterns and stewardship-related outcomes in surgical wards, with a concurrent focus on maintaining patient safety and clinical effectiveness.

METHODS AND ANALYSIS: We conducted a single-centre, quasi-experimental interrupted time-series study among adult patients admitted to the general and digestive surgery wards of a tertiary-care Spanish hospital. The study includes a retrospective pre-intervention period (1 January 2022-31 December 2023) and a prospective intervention period (1 April 2024-31 March 2026). The multimodal antimicrobial stewardship intervention comprises educational activities, updated local guidelines delivered via a dedicated web-based platform and mobile application, PAF on carbapenem prescriptions and structured reassessment of β-lactam allergy labels. The primary outcome is the temporal trend in monthly carbapenem consumption, expressed as defined daily doses per 100 patient-days. Secondary outcomes include temporal trends of monthly carbapenem days of therapy per 100 patient-days, overall antibiotic consumption, the proportion of patients receiving carbapenems and clinical safety outcomes (length of hospital stay, in-hospital mortality and 30-day readmission rates). In addition, the acceptance of stewardship recommendations, the accuracy of β-lactam allergy labelling and the monthly incidence of selected antimicrobial-resistant organisms, including Enterococcus faecium bloodstream infection and Clostridioides difficile infection, will be analysed. Aggregated data from routine clinical practice are extracted from electronic medical records, and pharmacy and microbiology databases, supplemented by anonymous surveys. Interrupted time-series regression models will be applied to assess changes in trends attributable to the intervention.

ETHICS AND DISSEMINATION: Approval for the protocol was granted by the Clinical Research Ethics Committee of Bellvitge University Hospital (PR332/23). The protocol complies with European and national data protection regulations. Findings will be disseminated through scientific conferences and publication in peer-reviewed journals.