Blood Cultures Time-to-Positivity as an Antibiotic Stewardship Tool in Immunocompromised Children with Gram-Negative Bacteraemia.

: Children and adolescents with haematologic malignancies or other causes of immunosuppression are at high risk of severe infections. Determining the probability of Gram-negative bacilli bloodstream infections (GNB-BSI) within 24 h of blood culture (BC) incubation could support early antibiotic de-escalation, compared to the current guidelines recommending de-escalation after 48-72 h. : Retrospective, observational single-centre study describing BC time-to-positivity (TTP) in GNB-BSI in a paediatric cohort of immunocompromised children. : In 128 episodes (100 patients), TTP was less than 24 h in >95% cases. TTP did not differ based on sex, underlying disease, degree of neutropenia, or PICU admission. Antibiotic initiation prior to BC collection and microbiological aetiology (microbiological aetiology different from , , , or ) were the only identified risk factors associated with BC growth beyond 24 h. No patients with late BC growth died or required PICU admission. : If BC remains negative after 24 h of incubation, GNB-BSI is unlikely in immunocompromised children and adolescents with fever. These results support early de-escalation strategies, shortening unnecessary exposure to broader-spectrum antibiotics, and potentially decreasing adverse events and costs.