Linezolid-resistant and vancomycin-resistant Enterococcus faecium urinary isolate in a pediatric B-ALL patient

Vancomycin-resistant Enterococcus faecium (VRE) is a major cause of healthcare-associated infections, especially in immunocompromised hosts. Linezolid is a key therapeutic agent due to its oral bioavailability and activity against resistant Gram-positive bacteria. While rare in U.S. pediatric patients, linezolid resistance can severely limit treatment options.

We describe a 16-year-old female with high-risk B-cell acute lymphoblastic leukemia whose hospitalization was complicated by urinary tract infection with VRE. Serial isolates tested on multiple antimicrobial susceptibility testing platforms yielded discordant results for linezolid susceptibility. Minimum inhibitory concentrations to linezolid and chloramphenicol increased together, suggesting potential ribosomal-target-mediated resistance. She ultimately required daptomycin therapy for linezolid-resistant VRE urinary tract infection treatment.

This case underscores the diagnostic challenges in detecting emerging linezolid resistance in E. faecium, particularly in immunocompromised patients. Accurate, timely susceptibility testing and improved access to confirmatory or molecular diagnostics are essential to guide therapy for VRE where linezolid remains one of the few viable therapeutic options.