Estimating changes in facility MRSA infection rates due to changes in MRSA precaution policy.

Abstract

The effectiveness of contact precautions (CP) and active surveillance (AS) for preventing methicillin-resistant Staphylococcus aureus (MRSA) in acute care remains uncertain. Some studies suggest CP reduces MRSA spread, while others report limited benefit. The COVID-19 pandemic disrupted MRSA prevention practices in the VA, creating an opportunity to assess their impact on MRSA healthcare-associated infections (HAIs). We studied 121 VA acute care hospitals from July 2020-June 2022. Facility practices (AS, CP for colonized [CPC], CP for infected [CPI]) were assessed via national surveys. Patient-level data identified MRSA HAIs (incident cultures ≥3 days post-admission). Secondary outcomes included sterile-site infections and 30-day post-discharge cultures. Associations between practices and HAI rates were estimated using Poisson, negative binomial, and mixed-effects Poisson regression, adjusting for baseline MRSA burden, COVID-19 admissions, culturing intensity, and hospital characteristics. Among 905,164 admissions, 1,708 incident MRSA cultures were identified. Many facilities suspended at least one prevention practice early in the pandemic, though most later reinstated them. In simpler models, discontinuation of AS, CPC, or CPI was associated with higher MRSA rates, but these associations were attenuated after adjustment for baseline burden. Mixed-effects models found no significant associations, and results were consistent across secondary outcomes. Discontinuation of MRSA prevention practices during the pandemic was not consistently linked to increased HAIs after accounting for baseline burden. Findings emphasize the role of facility-specific factors and modeling assumptions in evaluating infection control. Unmeasured pandemic-related practices (e.g., masking, PPE use) likely also influenced transmission, highlighting the need for flexible, context-sensitive, evidence-based infection prevention policies.