Antibiotic stewardship is important to address the problem of antimicrobial resistance, but a practical and sustainable strategy to provide stewardship in a large hospital setting is lacking. We developed a hospital-wide computerised antimicrobial approval system (HCAAS) to guide the use of antimicrobial agents in late 2004 in a 3500-bed medical centre in Taiwan. The objective of this study was to evaluate the impacts of HCAAS on the hospital from 2003 to 2009. Following HCAAS deployment, the gradients of consumption over time during the study period of third- and fourth-generation cephalosporins, fluoroquinolones and glycopeptides fell significantly, whilst that of carbapenems increased. The amount and expenditure of antimicrobial use did not increase with the overall healthcare-associated infection rate, and inpatient mortality rate remained stable with a slight decreasing trend. The rate of meticillin-resistant Staphylococcus aureus started to decline in 2002 and continued after HCAAS deployment. There was an increasing isolation of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae, presumably leading to the increased use of carbapenems. The isolation rate of Clostridium difficile from patients who developed diarrhoea after antimicrobial therapy did not change over the years, with a mean annual rate of 10.0% after the implementation of HCAAS. HCAAS along with strict infection control measures is necessary to reduce the spread of resistant organisms within the hospital. HCAAS is a sustainable system for providing antibiotic stewardship and exerts a positive impact on the hospital by reducing antimicrobial consumption and expenditure whilst not compromising healthcare quality.

• Quantitative data - Quantitative data were used during the intervention

• Human - All activities regarding organisations and individuals involved in health products and services

• Healthcare delivery