Effect of an antibiotic stewardship program on antimicrobial use and resistance in a high prescribing, high resistance setting: A single-center, interrupted time series analysis.

PURPOSE: To assess the impact of an antimicrobial stewardship (AMS) program on antimicrobial use and resistance rates in a tertiary care hospital situated in a region with high antimicrobial consumption and antimicrobial resistance (AMR) prevalence. METHOD: We conducted a quasi-experimental study, using interrupted time-series (ITS) design. The intervention consisted of a targeted prospective audit and feedback (PAF) strategy, in which the antimicrobial stewardship team (AST) was reviewing all prescriptions for carbapenems, colistin and tigecycline (i.e., "targeted" antimicrobials). We compared the period before (January 2014 - October 2016) and after the introduction of the PAF strategy (November 2016 - December 2019). The main metric of antimicrobial consumption was defined daily doses (DDDs) per 100 patient-days. RESULTS: ITS analysis showed that carbapenem consumption decreased significantly after the intervention [level change - 10.170 DDDs/100 patient-days (95% CI: -13.058, -7.282); p: <0.001] but remained stable thereafter [post-intervention yearly slope: 0.966 DDDs/100 patient-days (95% CI: -0.433, 2.366); p: 0.173]. Consumption of colistin and tigecycline also decreased significantly, however, ITS analysis showed an increasing trend in total antimicrobial consumption (yearly slope 0.668 DDDs/100 patient-days (95% CI: 0.162, 1.173; p: 0.010). Regarding carbapenem resistance, ITS analysis showed that after the PAF intervention there was a significant increase at level and a non-significant trend towards increase post-intervention. CONCLUSIONS: The implementation of PAF intervention in a setting with high antimicrobial consumption and resistance led to a significant reduction in the use of targeted antimicrobials, although total antimicrobial consumption showed an increasing trend. The effect of the AMS program on resistance rates was minimal. TRIAL REGISTRATION NUMBER: NCT04261348.