Evaluation of the Negative Predictive Value of Methicillin-Resistant Staphylococcus aureus Nasal Swab Screening in the Medical Intensive Care Units and Its Effect on Antibiotic Duration

BACKGROUND: In addition to active surveillance of methicillin-resistant Staphylococcus aureus (MRSA) carrier, MRSA nasal screening can be valuable for antibiotic de-escalation. This study aimed to assess the correlations between the MRSA nasal swab and subsequent culture results in patients admitted to medical intensive care units (MICU). The impact of MRSA nasal swab on the antibiotic duration was also evaluated. MATERIALS AND METHODS: This retrospective study enrolled patients who received glycopeptides in the MICU of a medical center in 2019. Patients treated with glycopeptides for over 2 days before MICU admission were excluded. The associated data were collected through the electronic medical record system. The negative predictive value (NPV) of MRSA nasal swabs for MRSA infection was calculated, and their influence on empirical glycopeptide treatment duration was analyzed. RESULTS: Of the 338 patients who met the inclusion criteria, 277 underwent MRSA nasal screening. The NPV of MRSA-negative nasal swab for subsequent MRSA infection was 98.4%. The glycopeptide treatment duration of the patients with and without nasal screening was not significantly different (4.2 ± 2.8 vs 4.4 ± 3.0 days, p = 0.577). Of the 120 patients with MRSA-negative nasal swab and no subsequent MRSA infection, 75 continued empirical glycopeptides therapy. The additional treatment time was 3 days (interquartile range: 2–6 days). CONCLUSION: The MRSA nasal swabs have high NPV for MRSA infection in critically ill patients. However, it has no impact on the empirical glycopeptide treatment duration. The value of MRSA nasal swabs should be advocated to optimize antibiotic therapy.