optrA-positive Enterococcus whole genome sequence

Enterococci are key opportunistic pathogens linked to healthcare-associated infections in pediatric patients. Linezolid, a World Health Organization (WHO)-designated critically important antibiotic for treating multidrug-resistant Gram-positive infections, now confronts the emergence of linezolid-non-susceptible enterococci (LNSE). However, data on the epidemiology and genomics of pediatric LNSE remain limited, impeding targeted infection control. We analyzed 26 LNSE strains isolated from Children’s Hospital, Zhejiang University School of Medicine (June 2020–July 2024). Strains were identified via MALDI-TOF MS and Vitek2 Compact; linezolid minimum inhibitory concentration (MIC) was determined by micro-broth dilution. Multilocus sequence typing (MLST), resistance/virulence gene detection, and pan-genome analysis (with COG/KEGG annotation) were also performed. Of the strains, 73.1% were from male patients and 42.3% from children ≥5 years. Enterococcus faecalis (E. faecalis) was predominant (88.5%), with ST16 as the dominant sequence type (ST) and four novel STs identified. All strains harbored optrA and fexA, while other resistance/virulence genes showed species specificity. The 23 E. faecalis strains had an open pan-genome (b=0.174725), with active horizontal gene transfer (HGT) and functional differentiation of core/accessory/unique genes. These findings confirm the rising prevalence of LNSE in pediatric patients, along with its species-specific traits and active HGT, providing essential data for targeted pediatric LNSE control.