Evaluating the Effectiveness of an Antimicrobial Stewardship Intervention on Reducing the Incidence Rate of Healthcare-Associated Clostridium difficile Infection

Background. The incidence rate of healthcare-associated Clostridium difficile infection (HA-CDI) is estimated at 1 in 100 patients. Antibiotic exposure is the most consistently reported risk factor. Strategies to reduce HA-CDI have focused on reducing antibiotic utilization. Prospective audit and feedback (PAF) is a commonly used antimicrobial stewardship intervention (ASi). The impact of this ASi on HACDI is equivocal. This study examines the impact of a PAF ASi on the incidence of HA-CDI. Methods. Single-site, 339 bed community-hospital in Ontario, Canada. Primary outcome is HA-CDI incidence rate. Daily PAF ASi is the exposure variable. PAF ASi is implemented across wards in a non-randomized stepped wedge design starting in July 2013. Criteria for ASi; any intravenous antibiotic use for ≥48 hours, or any fluoroquinolone or cephalosporin use for ≥48 hours. HA-CDI cases and model covariates aggregated by ward and month. Pooled statistical analyses done using generalized linear models with log link function. Potential clustering by ward and serial correlation of HA-CDI accounted for in final model. Other covariates tested for inclusion in final model were derived from previously published risk factors. Final pooled model was compared with random coefficient model (RCM). Goodness-of-fit (GOF) assessed using deviance statistics. Results. N = 430 observations with ASi implemented in 64 periods. The final model included; ASi, days of antibiotic therapy (DOT), previous month’s CDI cases (LCDI), current month’s community-associated-CDI cases (CA-CDI), length of stay (LOS) and days of hospitalization due to age over 65 years (Age), and interaction terms between ASi-DOT, LOS-Age and ASi-LCDI. ASi incidence rate ratio (IRR) is 0.42 (95% CI, 0.19–0.92). ASi-DOT interaction IRR was not significant. LCDI IRR was 1.20 (95% CI, 1.07–1.35) and CA-CDI IRR was 1.26 (95% CI, 1.12–1.42). Pooled model was equivalent to RCM and provided excellent GOF. Conclusion. Daily PAF ASi resulted in a significant reduction in HA-CDI; however, this effect was not mediated by an overall reduction in antibiotic utilization. In addition, the importance of CDI environmental pressure was demonstrated through the significant impact of both CA-CDI and LCDI on subsequent HA-CDI incidence rates. Disclosures. All authors: No reported disclosures.