 Background: Antimicrobial stewardship program ASP is recommended to improve appropriate antimicrobial use, reduce bacterial resistance, unnecessary drug costs and enhance patient health outcomes. Two core strategies of ASP recommended as effective in guidelines are formulary restriction with drug preauthorization and prospective audit with feedback. Preauthorization is the current strategy used in our hospital, while most other hospitals in Taiwan and worldwide uses prospective audit with feedback. Preauthorization requires intensive manpower to maintain timeliness of antimicrobial use. This study will evaluate a policy change in strategy used for antimicrobial stewardship. Investigators will evaluate the effectiveness of the 2 strategies using antimicrobial utilization and patient outcomes. 