In vitro activity of contezolid against gram-positive bacteria isolated from pediatric patients with invasive infections.

Contezolid, a novel oxazolidinone, exhibits potent activity against multidrug-resistant gram-positive pathogens, but data in pediatric populations remain limited. This study evaluated the in vitro activity of contezolid against Streptococcus pneumoniae (n = 53) and Staphylococcus aureus (n = 92) isolates recovered from sterile-site specimens of pediatric patients with invasive infections (2018-2023). MICs were determined by broth microdilution. For S. pneumoniae, contezolid MICs ranged from 0.125 to 1.000 µg/mL (MIC50/90, 0.250/0.500 µg/mL), with comparable activity against penicillin-susceptible and penicillin-nonsusceptible isolates. Contezolid exhibited low MIC values with a relatively narrow distribution across serotypes and specimen sources, without marked differences. For S. aureus, contezolid MICs ranged from 0.250 to 2.000 µg/mL (MIC50/90, 0.500/1.000 µg/mL), with equivalent activity against methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). All isolates were susceptible, with most MICs ≤ 0.500 µg/mL and a minority (n = 25) at 1-2 µg/mL, mostly involving isolates from blood. Contezolid exhibited potent and consistent in vitro activity against gram-positive pathogens isolated from invasive infections in pediatric patients, including MRSA and PNSP, with stable susceptibility profiles across major clonal lineages. These findings demonstrate favorable in vitro activity of contezolid against clinically significant isolates.IMPORTANCEThis study provides an evaluation of the in vitro activity of contezolid against gram-positive bacterial isolates obtained exclusively from pediatric patients with invasive infections. By characterizing susceptibility patterns across resistance phenotypes and molecular backgrounds, our findings offer important baseline data to inform future clinical studies of contezolid in pediatric populations.