Impact of MRSA Nasal Screening in Lower Respiratory Tract Infections: A Systematic Review Incorporating Network and Bayesian Meta-Analyses

Background Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia requires empirical therapy coverage for patients with risk factors, yet MRSA causes <1% of community-acquired and 20-40% of nosocomial pneumonias. MRSA polymerase chain reaction (PCR) nasal screening offers rapid results with 95-99% negative predictive value. We systematically evaluated clinical outcomes associated with MRSA nasal screening in hospitalized patients with lower respiratory tract infections (LRTIs). Methods We searched PubMed and EMBASE through June 29th, 2024 for studies evaluating MRSA nasal screening in adult inpatients with LRTIs. The primary outcome was duration of MRSA therapy. Secondary outcomes included frequency of vancomycin trough monitoring, hospital length of stay, incidence of acute kidney injury (AKI), in-hospital mortality, and 30-day readmission. We performed frequentist and Bayesian meta-analyses. Results Fifteen studies (2,872 patients) were included. Pharmacist-driven protocols (PDP) with PCR versus standard of care significantly reduced MRSA therapy duration (mean difference -1.34 days, 95% CI -1.59 to -1.08; I2=61%). Network meta-analysis showed PDP+PCR was most effective (-1.51 days vs no testing, 95% CI -2.04 to -0.98), while PCR or culture alone showed no significant benefit. PDP+PCR reduced vancomycin trough monitoring (OR 0.21, 95% CI 0.13-0.33), AKI (OR 0.54, 95% CI 0.39–0.76), and in-hospital mortality (OR 0.70, 95% CI 0.50 to 0.96). Bayesian analysis showed >99% probability of exceeding minimal clinically important differences for duration of MRSA therapy and trough monitoring, but 36% or less for other outcomes. Conclusion MRSA nasal PCR screening with pharmacist-driven protocols significantly reduces MRSA therapy exposure and improves clinical outcomes in hospitalized LRTI patients, supporting broader implementation of this diagnostic-antimicrobial stewardship synergy.