Effects of Antibiotic Stewardship Program on Antibiotic Consumption and the Incidence of Clostridioides difficile Infection

Background/Objectives: Growing concerns about antibiotic-associated adverse events, including Clostridioides difficile infection, prompted implementation of an antibiotic stewardship program (ASP) in South Korea in November 2024. One year post-implementation, we evaluated changes in antibiotic consumption and C. difficile infection incidence. Methods: This study was conducted at Chung-Ang University Gwangmyeong Hospital, South Korea. Segmented regression and interrupted time series analyses were performed using weekly data on antibiotic use (days of therapy [DOT] per 1000 patient-days) and C. difficile infection or colonization (cases per 1000 patient-days) over 157 weeks (November 2022–October 2025). Weeks 1–105 defined the pre-ASP period, and weeks 106–157 the post-ASP period. A 4-week lag between antibiotic use and subsequent C. difficile infection was hypothesized. Results: Before ASP, weekly total antibiotic use increased (β1 = 1.14, 95% CI, 0.76 to 1.51, p < 0.001). After ASP, the slope decreased significantly (β3 = −1.50, 95% CI −2.62 to −0.39, p = 0.009), consistent across anti-pseudomonal penicillins and cephalosporins and fluoroquinolones. Pre-ASP C. difficile incidence increased (α1 = 0.01, 95% CI, 0.01 to 0.02, p < 0.001); the upward trend attenuated post-ASP, though slope change was not significant (α3 = −0.01, 95% CI, −0.03 to 0.004, p = 0.13). An increase of 1 DOT per 1000 patient-days was associated with a 0.005-case increase in C. difficile infection incidence after 4 weeks. Conclusions: The observed effects of proactive ASP strategies underscore the importance of maintaining stewardship in clinical practice. Further studies are warranted to assess the sustainability of these findings and evaluate additional factors influencing C. difficile infection incidence.