432. Ward-level Variation in Transmission of MRSA in Veterans Affairs Hospitals


 
 
 In 2007, the Department of Veterans Affairs (VA) implemented the methicillin-resistant Staphylococcus aureus (MRSA) Prevention Initiative nationally in acute care facilities (ACFs). Since that time, numerous publications have reported declining transmission rates and infection rates due to MRSA across the VA. Recent estimates of the impact of contact precautions (CP) on transmission suggest that the infectiousness of patients while on CP was 50% lower than patients not on CP. We extend that work by estimating the variation and trend in transmission while accounting for the estimated impact of CP on transmission.
 
 
 
 We analyzed ten years of data from 108 VA ACFs from 1/1/2008 – 12/31/2017 using a Bayesian transmission model. The data included admission, discharge, and surveillance and clinical test results for MRSA. Data were partitioned into five 2-year analysis periods to allow for estimates of transmission to change over time, including all facilities with complete data spanning the 10-year study period. We estimated person-to-person transmission rates for each ward assuming the classic mass-action transmission framework, while accounting for the impact of CP on transmission, and used random effect models with inverse variance weights to derive pooled estimates of the transmission rates and trends across ward-types and over time.
 
 
 
 In this cohort study of 108 VA hospitals during the 10-year period, more than 2 million unique individuals had over 5.6 million admissions with more than 8.4 million MRSA surveillance tests (9.3% of which were positive). We observed a decline in the overall transmission rate over time, with the reduction driven by declining rates of transmission in the ICU setting (Figure 1). We observed that the transmission rate in medical/surgical wards remained constant during the 10-year period.
 Transmission trend by ward
 
 
 
 We observed that in addition to the two-fold reduction in transmission of MRSA associated with CPs, that over the study period, the transmission rate declined in VA hospitals driven largely by reductions in the ICU setting. The secular trend downward in ICUs might reflect improved hand hygiene, changes in antibiotic use, or enhancements to other infection control practices. Additional work is needed to better understand and identify these factors.
 
 
 
 Karim Khader, PhD, BioFire Diagnostics: Grant/Research Support.
