Impact evaluation of an antimicrobial stewardship team intervention based on AWaRe guidelines: a single- center, cohort, interrupted-time series study

Background The global crisis of antimicrobial resistance (AMR) necessitates robust antimicrobial stewardship. The World Health Organization's (WHO) Access, Watch, Reserve (AWaRe) classification is a key tool for guiding antibiotic prescribing to combat AMR. The WHO’s global target was to have at least 60% of antibiotic consumption fall into the Access category by 2023. This study evaluated the effectiveness of localized interventions toward this goal. Methods This retrospective, longitudinal study analyzed oral outpatient antibiotic prescriptions at Kochi Medical School Hospital from April 2022 to June 2025. Data included defined daily doses (DDDs), days of therapy (DOTs), and AWaRe classifications. Based on a preceding analysis, the antimicrobial stewardship team (AST) implemented targeted, department-specific educational interventions starting in April 2024. The impact was evaluated using time-series analysis and regression models. The study also included a survey of Escherichia coli susceptibility to levofloxacin, ciprofloxacin, and trimethoprim-sulfamethoxazole from outpatient urinary isolates. Results The AST intervention led to a statistically significant increase in the usage proportion and DDDs of Access antibiotics (p = 0.02 and p = 0.0005, respectively), with a corresponding decrease in Watch antibiotics (p = 0.02). However, DOTs did not significantly change, indicating the intervention primarily impacted drug choice, not treatment duration. Top prescribed agents were clarithromycin (24.2%), sulfamethoxazole/trimethoprim (20.7%), and rifaximin (10.7%). E. coli susceptibility to levofloxacin and ciprofloxacin was low (< 80% overall), particularly in extended-spectrum β-lactamase (ESBL)-producing strains (~ 10%). Sulfamethoxazole/trimethoprim susceptibility remained high overall (≥ 80%) but was low (< 80%) for ESBL-producing strains. Conclusions AST interventions successfully shifted outpatient prescribing from Watch to Access antibiotics, demonstrating that targeted interventions can modify prescribing behavior. However, challenges remain, such as addressing treatment duration and achieving broader goals. The observed resistance patterns highlight the critical need for prescribers to consult local antibiograms. Future strategies require a more comprehensive approach, including real-time alerts and improved diagnostics, to further optimize antibiotic use and combat AMR.