Long-term outcomes of an antimicrobial stewardship program implemented in a hospital with low baseline antibiotic use.

OBJECTIVE: To evaluate the long-term outcomes of an antimicrobial stewardship program (ASP) implemented in a hospital with low baseline antibiotic use.
DESIGN: Quasi-experimental, interrupted time-series study.
SETTING: Public safety net hospital with 525 beds. INTERVENTION: Implementation of a formal ASP in July 2008.
METHODS: We conducted a time-series analysis to evaluate the impact of the ASP over a 6.25-year period (July 1, 2008-September 30, 2014) while controlling for trends during a 3-year preintervention period (July 1, 2005-June 30, 2008). The primary outcome measures were total antibacterial and antipseudomonal use in days of therapy (DOT) per 1,000 patient-days (PD). Secondary outcomes included antimicrobial costs and resistance, hospital-onset Clostridium difficile infection, and other patient-centered measures.
RESULTS: During the preintervention period, total antibacterial and antipseudomonal use were declining (-9.2 and -5.5 DOT/1,000 PD per quarter, respectively). During the stewardship period, both continued to decline, although at lower rates (-3.7 and -2.2 DOT/1,000 PD, respectively), resulting in a slope change of 5.5 DOT/1,000 PD per quarter for total antibacterial use (P=.10) and 3.3 DOT/1,000 PD per quarter for antipseudomonal use (P=.01). Antibiotic expenditures declined markedly during the stewardship period (-$295.42/1,000 PD per quarter, P=.002). There were variable changes in antimicrobial resistance and few apparent changes in C. difficile infection and other patient-centered outcomes.
CONCLUSION: In a hospital with low baseline antibiotic use, implementation of an ASP was associated with sustained reductions in total antibacterial and antipseudomonal use and declining antibiotic expenditures. Common ASP outcome measures have limitations.