Impact of an Antimicrobial Stewardship Program on Antimicrobial Utilization, Bacterial Susceptibilities, and Financial Expenditures at an Academic Medical Center.

Background: Antimicrobial stewardship programs (ASPs) have the potential to improve patient outcomes, decrease microbial resistance, increase patient safety, and decrease costs. However, to justify the costs involved with providing an ASP, it is necessary to assess its impact in achieving these outcomes on an ongoing basis. Objective: The purpose of this study was to characterize the overall impact of the ASP at an Academic medical center. Methods: Quasi-experimental, before and after stewardship program implementation, retrospective analyses of quarterly antimicrobial utilization, bacterial susceptibilities, and antibiotic acquisition costs were utilized. Results: Mean stewardship-focused antibiotic utilization was 510.3 defined daily doses (DDD) per 1,000 patient days for the pre-ASP period and 426.4 DDD per 1,000 patient days for the ASP period (16.4% decrease; p < .001). Significant changes in Pseudomonas aeruginosa susceptibility to tobramycin (8% increase; p = .006) and piperacillin-tazobactam (8% decrease; p = .024) were noted. Changes in susceptibility of Staphylococcus aureus to methicillin (7% increase, p = .012) were also observed. ASP-focused antibiotic expenditures decreased from $4,028,068 in fiscal year (FY) 2010 to $2,135,173 in FY2013 (p = .01). Conclusions: ASP initiatives were associated with an observed reduction in stewardship-focused antibiotic utilization. Significant changes in susceptibilities of some bacteria were noted but did not seem to consistently reflect antibiotic utilization changes. Significant decreases in antimicrobial expenditures were observed. Observed outcomes are temporally related to shifts in antimicrobial selection through the initiation of stewardship program-driven antibiotic policy changes. These outcomes have been used to justify and expand our stewardship program moving forward.