Detection of Pathogens in the Gut Microbiome Prior to Bloodstream Infection in Children with Acute Myeloid Leukemia or Mature B-Cell Non-Hodgkin Lymphoma

Background: Bloodstream infections (BSIs) cause significant morbidity and mortality in children with hematological malignancies. The gut may serve as a potential reservoir for BSI-causing bacteria. Therefore, this longitudinal study aimed to assess the abundance of BSI-causing bacterial strains in the gut microbiota prior to BSI. Methods: This prospective longitudinal cohort study included children (1-18 years) diagnosed with acute myeloid leukemia or mature B-cell non-Hodgkin lymphoma. Fecal samples were collected twice weekly, and additionally whenever a BSI was suspected. Gut microbiota were profiled at species level using the PCR-based assay Molecular Culture. Results: We recruited 26 children, of whom 16 experienced a total of 31 BSI episodes. In total, 18 out of 38 BSI pathogens (47.4%) could be detected in fecal samples prior to BSI. In the BSI episodes caused by enteric bacteria, 75% of all causative enteric bacteria could be found prior to BSI. Also, bacteria not typically associated with the gut could be detected prior to BSI in feces (Streptococcus mitis in 100% of cases, Staphylococcus epidermidis in 29% of cases). Furthermore, in fecal samples collected after BSI onset and start of antibiotic treatment, 58% of the BSI pathogens could be detected. Conclusions: BSI pathogens, both gram-negative and gram-positive, can be detected in the gut microbiome prior to BSI, and an increase in relative abundance is related to BSI. Secondly, BSI pathogens may persist despite BSI-directed intravenous antibiotic therapy, potentially preceding future BSIs.