Background and objectives:
Antimicrobial stewardship (AMS) programs aim to reduce healthcare-associated infections (HAIs) and save healthcare costs associated with antimicrobial resistance (AMR). This study aims to evaluate the economic and social burden of HAIs before and after the implementation of AMS programs, including the use of new antibiotics.

Methods:
The study was divided in two phases. In the first phase, the analysis was carried out considering the administrative database of the hospital discharge records from 2006 to 2019. HAIs were detected by selecting all acute hospitalizations with primary or secondary diagnosis related to Escherichia coli, Klebsiella spp, Clostridium difficile, and other unspecified bacterial infections. Data were used to estimate prevalence of HAIs and their impact in terms costs incurred by the NHS. In the second phase, three key opinion leaders (KOLs) were involved: a questionnaire was used to collect additional data on the three Hospital antimicrobial stewardship (AMS) programs, the number of HAIs before and after introducing programs and new antibiotics. Finally, interviews were used to explore the views and experiences of KOLs on AMS and the use of new antibiotics.

Results:
HAIs appear on average in 32 cases per 1,000 acute hospitalizations. The occurrence of infections is increasing (22.5 per 1,000 hospitalizations in 2006 and 44.8 per 1,000 in 2019). The valuation of infections resulted in an average annual estimate of approximately € 397 million. The second phase is still ongoing. Preliminary results show a reduction of length of hospital stay (mean 25%, range 14-40%), treatment duration (24%; 14-30%) and antibiotics consumption in DDD (29%; 14-46%).

Conclusion:
AMS is a crucial component in the overall effort to combat the spread of AMR. The preliminary results show that implementation of AMS programs reduced antimicrobial use and cost, and lowered the incidence of HAIs.