(623) Evaluation of the NPV of MRSA Nasal Swab Screening in a PICU and Its Impact on Antibiotic Duration

Introduction: MRSA nasal colonization can be accurately detected with nasal swab polymerase chain reaction (PCR). Negative predictive value (NPV) of a negative MRSA nasal swab for subsequent MRSA infection has been shown to be greater than 98% when ruling out suspected MRSA pneumonia, intra-abdominal infections, and bacteremia, which can be valuable to guide antibiotic de-escalation. This study aimed to assess overall usage of MRSA-active agents in the pediatric intensive care unit (PICU), defined as days of therapy (DOT), before and after implementation of focused education encouraging MRSA nasal swab for patients initiating MRSA-active agents. The correlation between MRSA nasal swab and subsequent culture results was also evaluated.

Methods: A retrospective review was conducted of patients in the PICU in the year preceding intervention (January-November 2023) and 8 months post-intervention (December 2023-July 2024) that received a MRSA-active agent. Demographic data were collected in addition to indication for initiation of empiric antibiotics. Frequency of MRSA nares swabs and duration of therapy of MRSA active-agents, particularly vancomycin, was analyzed. The NPV of MRSA nasal swabs for MRSA infection was calculated.

Results: During the study period there were 310 patients treated with vancomycin and 66 who underwent MRSA nares screening. There was an 34.6% absolute increase in MRSA nares screening following the educational intervention (53/66 vs. 13/66). The average pre-intervention vancomycin DOT per month was 122.9 days compared to 90.6 days post-intervention, resulting in a 26.3% decrease in total vancomycin DOT after intervention. Fifty-eight of the sixty-six patients with MRSA nasal swabs had a blood or bacterial culture performed, of which three were positive for MRSA. The NPV of negative MRSA nasal swab for subsequent MRSA infection was 98.2%.

Conclusions: Use of MRSA nasal swab PCR led to a decrease in vancomycin DOT in the PICU without adverse clinical outcomes. For critically ill pediatric patients in our PICU, MRSA nasal swab had high NPV for MRSA infection. MRSA nasal swabs should be considered to guide antibiotic de-escalation.