The epidemiological landscape of bloodstream infections in children undergoing chemotherapy or haematopoietic cell transplantation: A retrospective study by Infectious Diseases Working Group of Italian Association of Pediatric Hematology and Oncology (AIEOP).

Understanding bloodstream infection (BSI) epidemiology is crucial for optimizing antibiotic therapy in paediatric haematology-oncology patients undergoing chemotherapy or haematopoietic cell transplantation (HCT). However, updated paediatric data remain scarce. This multicentre retrospective study analysed BSI epidemiology across 22 Italian centres (2018-2019), assessing pathogens, resistance profiles, empirical antibiotic therapy (EAT) and clinical course with outcomes. Mortality risk factors were evaluated using a Cox regression model. A total of 510 BSI episodes occurred in 396 patients (median age 6.4 years), with an incidence of 2.9 and 5.1 per 1000 inpatient days for chemotherapy and HCT respectively. Multidrug-resistant (MDR), third to fourth generation cephalosporin- and carbapenem-resistant, account for 18.3%, 29.3% and 8.2% of Gram-negative infections respectively. 42.2% of Klebsiella pneumoniae isolates were MDR. Combination EAT was used in 269/510 episodes, with piperacillin-tazobactam+amikacin being most common. Microbiological appropriateness was 82%. Infection-related and 30-day mortality rates were 4.1% and 5.29%, respectively, with appropriate EAT significantly reducing mortality. Our findings highlight the burden of resistant pathogens in paediatric BSIs and emphasize the importance of appropriate EAT in improving outcomes, underscoring the need for treatment strategies tailored to local resistance patterns.