In-hospital antibiotic consumption in Lombardy, Italy (2017–2024): a retrospective analysis of regional administrative data

Introduction: Antimicrobial stewardship (AMS) is essential to tackle antimicrobial resistance. Antibiotic consumption (AC) surveillance provides evidence to guide AMS interventions. This study investigated in-hospital AC trends in Lombardy, Italy (2017-2024), with particular focus on the impact of COVID-19. Methods: AC was expressed as DDDs per 100 bed days (absolute AC), relative proportions of Access/Watch/Reserve antibiotics (relative AC), Access-to-Watch index, and Access-to-(Watch + Reserve) index. Analyses were stratified by ward type-medical (MUs), surgical (SUs), and intensive care units (ICUs)-and timeframes: pre-COVID-19 (01/2017-02/2020), COVID-19 onset (02-03/2020), COVID-19 (03/2020-05/2023), and post-COVID-19 (05/2023-12/2024). Results: Despite a surge in total AC in 2017-2024, relative Access AC rose while relative Watch AC declined, resulting in an increase of the Access-to-Watch and Access-to-(Watch + Reserve) indexes, except in ICUs. A transient reversal of such favourable trends was observed at COVID-19 onset. Nevertheless, the WHO 2023 target of ≥60% total AC being Access was not achieved; furthermore, Access-to-Watch and Access-to-(Watch + Reserve) indexes constantly remained <1, except for SUs. A downward trend in Access-to-Watch and Access-to-(Watch + Reserve) indexes was registered in the post-pandemic period. Reserve AC increased across time, periods and wards, exceeding the expected levels obtained using projections from pre-COVID-19 data. Conclusions: These findings highlight substantial shifts in in-hospital AC in Lombardy during the period 2017-2024, with concerning increases in Reserve antibiotics and an enduring failure to meet the 2023 WHO target of ≥60% Access antibiotics especially in MUs and ICUs, underscoring the need for reinforced AMS policies in the post-pandemic era.