Phylotype ratios included.

<div> Background Surveillance cultures to identify patients colonized with methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) is recommended at pediatric intensive care unit (PICU) admission but doesn’t capture other methicillin-resistant <i>Staphylococcus</i> and is resource intensive. We determined the prevalence and identified nasal microbiome predictors for methicillin-resistant <i>Staphylococcus</i> colonization at the time of PICU admission. Study design A prospective cohort study was performed in a 20-bed pediatric intensive care unit (PICU) between 2020–2021. Anterior nares nasal swabs processed for MRSA culture, nasal microbiome and <i>mecA+</i> qPCR were obtained within first five days after PICU admission. Predictive values of methicillin-resistant <i>Staphylococcus</i> carriage on symptoms of infection and for nasal microbiome attributes were calculated. Results A total of 5 (8.0%) of 62 patients had a nares culture positive for MRSA and 22 (35.5%) of 63 patients had methicillin-resistant <i>Staphylococcus</i> (MRSA or methicillin-resistant coagulase-negative <i>Staphylococci</i>). In univariate analysis, carriage with MRSA or MRCoNS was associated with having a fever during PICU stay. Colonization with a distinct set of microbes (including <i>Haemophilus</i>, <i>Streptococcus</i>, <i>Prevotella</i> and <i>Corynebacterium</i> sp.) was predictive of having methicillin-resistant <i>Staphylococcus</i> colonization. Conclusions Carriage with methicillin-resistant <i>Staphylococcus</i> may lead to transmission in critically ill pediatric patients. Carriage of particular nasal microbes appears to facilitate colonization with methicillin-resistant <i>Staphylococcus</i>. </div>