Impact of California's mandate for antimicrobial stewardship programs on rates of methicillin-resistant Staphylococcus aureus and Clostridioides difficile infection in acute-care hospitals.

OBJECTIVE: To estimate the impact of California's antimicrobial stewardship program (ASP) mandate on methicillin-resistant Staphylococcus aureus (MRSA) and Clostridioides difficile infection (CDI) rates in acute-care hospitals. POPULATION: Centers for Medicare and Medicaid Services (CMS)-certified acute-care hospitals in the United States. DATA SOURCES: 2013-2017 data from the CMS Hospital Compare, Provider of Service File and Medicare Cost Reports. METHODS: Difference-in-difference model with hospital fixed effects to compare California with all other states before and after the ASP mandate. We considered were standardized infection ratios (SIRs) for MRSA and CDI as the outcomes. We analyzed the following time-variant covariates: medical school affiliation, bed count, quality accreditation, number of changes in ownership, compliance with CMS requirements, % intensive care unit beds, average length of stay, patient safety index, and 30-day readmission rate. RESULTS: In 2013, California hospitals had an average MRSA SIR of 0.79 versus 0.94 in other states, and an average CDI SIR of 1.01 versus 0.77 in other states. California hospitals had increases (P < .05) of 23%, 30%, and 20% in their MRSA SIRs in 2015, 2016, and 2017, respectively. California hospitals were associated with a 20% (P < .001) decrease in the CDI SIR only in 2017. CONCLUSIONS: The mandate was associated with a decrease in CDI SIR and an increase in MRSA SIR.