Methicillin-resistant Staphylococcus aureus nasal swabs: trends in use and association with outcomes.

Objective: To investigate patterns of early methicillin-resistant Staphylococcus aureus (MRSA) nasal swab use in US hospitals and the association with de-escalation of MRSA-specific antibiotics.

Design: Retrospective cohort study.

Setting: PINC-A1 Healthcare Database (2008-2021).

Participants: Adults with sepsis present on admission who received invasive mechanical ventilation by hospital day 1.

Methods: We assessed interhospital variation and time trends in early polymerase chain reaction-based MRSA nasal swab use using bivariable regression. Next, we used competing risks multivariable regression to assess the association of early (started by hospital day 2) anti-MRSA antibiotic duration with care in a high (≥90%) versus low (<10%) swab use hospital.

Results: We included 699,474 patients across 788 hospitals to evaluate trends in early swab use; 151,205 (21.6%) received a swab. Use of swabs varied across hospitals (median use: 6.0% [interquartile range: 0-37.6%; full range: 0%-98.0%]; median odds ratio [95% CI]: 84.7 [63.3-115.6]) and overall use increased over time (3.5% in 2008 quarter 1 increasing to 29.5% in 2021 quarter 4; regression coefficient [95% CI]: 0.14% [0.12%-0.15%]). Considering 41,599 patients (9,796 [23.6%] in 33 hospitals where ≥90% received swabs and 31,763 [76.4%] in 67 hospitals with <10% use), anti-MRSA antibiotic durations were shorter in hospitals where ≥90% (vs < 10%) received a swab (adjusted sub-hazard ratio for discontinuation of antibiotics [95% CI]: 1.17 [1.04-1.31], P = .007).

Conclusions: Use of early polymerase chain reaction-based MRSA nasal swabs varied across US hospitals and increased over time. Receiving care in a hospital with higher swab use was associated with shorter anti-MRSA antibiotic duration.