Risk factors of bloodstream infection after allogeneic hematopoietic cell transplantation in children/adolescent and young adults.

Allogeneic hematopoietic cell transplantation (HCT) is a crucial treatment for various diseases, including hematological malignancies, solid tumors, and genetic disorders. Despite its curative potential, HCT is associated with severe complications, notably infections, graft-versus-host disease, and organ damage. Infections, particularly bloodstream infections (BSIs), pose a significant threat in the initial weeks post-HCT, necessitating effective management strategies. This retrospective study aimed to clarify the incidence, pathogens, and risk factors associated with BSI within the first 30 days after allogeneic HCT in children/adolescents and young adults (AYAs). The study included 115 patients aged <31 years who underwent 121 allogeneic HCTs at the Department of Pediatrics, Nagoya University Hospital between January 1, 2018, and March 31, 2022. Data encompassed demographic characteristics, HCT details, and BSI information. Overall, 27 of 121 patients developed BSI with the cumulative incidence of 23.5% (95% confidence intervals [CI]: 17.0%-30.6%) at 30 days after HCT. The median onset time of BSI was 7 (range, 4-26 days) after HCT. Gram-positive bacteria accounted for 89% of pathogens isolated from blood cultures, with Streptococcus mitis/oralis being the most common. In multivariable analysis, tandem HCT (subdistribution hazard ratio [SHR]: 5.67, 95% CI: 2.74-11.7, p < 0.001) and peripherally inserted central catheters (SHR: 2.96, 95% CI: 1.34-6.55, p  =  0.007) were identified as independent risk factors for BSI. In patients receiving tandem HCT, the pathogens isolated from blood cultures were all gram-positive bacteria, with Streptococcus mitis/oralis accounting for up to 67% of the isolated pathogens. Tandem HCT and PICCs were identified as independent risk factors for BSI after allogeneic HCT in children/AYAs. The pathogens were commonly gram-positive, and Streptococcus mitis/oralis is important in patients who received tandem HCT. These data can provide valuable information for future studies to consider effective interventions to reduce the risk of BSI in high-risk patients.