Evaluating Methicillin-Resistant Staphylococcus aureus Polymerase Chain Reaction Nasal Screening as a Tool for...

Area of Science:

• Infectious Diseases
• Clinical Microbiology
• Hospital Epidemiology

Background:

• Broad-spectrum antibiotics are frequently initiated for suspected infections in hospitalized adults.
• Antimicrobial stewardship is crucial due to negative effects of inappropriate antibiotic use.
• Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nasal screening shows utility in pneumonia management.

Purpose of the Study:

• To evaluate the effectiveness of MRSA PCR nasal swabs in ruling out MRSA infections across all sources in hospitalized patients.
• To assess the potential of MRSA nasal screening to guide the de-escalation of empiric anti-MRSA antibiotics.

Main Methods:

• A single-center retrospective chart review of adult patient encounters from October 2019 to July 2021.
• MRSA PCR nasal testing was performed on all included patients.
• Infections were identified via source cultures, serving as the gold standard; diagnostic accuracy metrics were calculated.

Main Results:

• MRSA nasal swabs demonstrated a high negative predictive value (NPV) for various MRSA infections, including 100% for urinary tract infections and 97.8% for pneumonia.
• Overall, MRSA PCR nasal swabs showed a sensitivity of 68.5%, specificity of 90.1%, and an overall NPV of 98.5% for any MRSA infection.
• The prevalence of MRSA nasal carriage was 12%, and MRSA infection was present in 7.5% of all infections.

Conclusions:

• MRSA PCR nasal swabs possess a high NPV, supporting their use to rule out MRSA infections.
• Implementing MRSA nasal screening can facilitate early de-escalation of MRSA coverage, potentially decreasing antibiotic-associated morbidity, resistance, and healthcare costs.
• Further studies are recommended to validate these findings and support broader implementation.