# The clinical utility of nasal MRSA PCR as an antimicrobial stewardship tool to guide MRSA bacteraemia therapy in paediatrics: a retrospective study at a tertiary care centre

## TL;DR

This study shows that nasal MRSA PCR can help guide antibiotic use in children with suspected MRSA infections, reducing unnecessary treatments.

## Contribution

The study evaluates nasal MRSA PCR as a novel antimicrobial stewardship tool in pediatric MRSA bacteraemia.

## Key findings

- Nasal MRSA PCR had a 99.8% negative predictive value, indicating high reliability for ruling out MRSA.
- Among patients with systemic inflammatory response syndrome, the positive predictive value increased to 9%.
- Unnecessary anti-MRSA therapy was linked to higher mortality in patients without confirmed MRSA.

## Abstract

Vancomycin is the main therapeutic choice for paediatric methicillin-resistant Staphylococcus aureus (MRSA) infections. However, its use is associated with many clinical challenges. This study aimed to investigate the use of MRSA polymerase chain reaction (PCR) as an antimicrobial stewardship tool to enhance therapeutic decision-making in paediatric MRSA bacteraemia.

This retrospective cohort study was conducted at a tertiary healthcare centre from January 2021 to January 2024. It included paediatric patients who were screened for MRSA nasal colonization via PCR and had a blood culture obtained within 7 days of the MRSA PCR collection date. Clinical characteristics were compared between the positive and negative PCR groups. Positive and negative predictive values were determined. The association between mortality and anti-MRSA therapy was explored for patients with no confirmed MRSA infection.

A total of 1136 PCR tests were analysed with 161 positive results. The positive PCR group had a higher proportion of patients with intensive care unit admission, inotropic support and absolute neutrophil count >500. The positive PCR group had a higher proportion of patients who received anti-MRSA therapy, although no significant difference was observed in the therapy duration between the groups. The nasal MRSA PCR showed a positive predictive value (PPV) of 5.6% and a negative predictive value of 99.8%. When the analysis was restricted to patients with paediatric systemic inflammatory response syndrome, the PPV increased to 9%. Among patients who had negative PCR and culture results, a higher risk of mortality was observed for those using anti-MRSA therapy.

Nasal MRSA PCR may serve as a valuable component of antimicrobial stewardship programmes to optimize the prescribing practices of anti-MRSA therapy.