Markers of NETs including extracellular DNA (ecDNA), myeloperoxidase (MPO) and cathelicidin were analyzed in children with febrile UTI caused by E.coli (n = 98, aged 0.3–1.3 years) and in healthy controls (n = 50, 0.5–5.2 years). The gene discussed is MPO; the disease is bacterial urinary tract infection.