Abstract
BACKGROUND: Infections are the leading cause of non-relapse mortality in pediatric hematopoietic cell transplant (HCT) recipients. Up to 90% of bacteremias in these patients originate from gut microbiome organisms. However, selection for resistance genes, such as Extended-spectrum β-lactamase (ESBL), in these patient's gut microbiomes remains poorly understood. METHODS: Stools were prospectively collected from pediatric HCT recipients at multiple centers (n=133 patients, five centers) on the day of HCT, the day of neutrophil engraftment, and 30 days post-HCT. Bacterial DNA was isolated and sent for shotgun metagenomic sequencing. Antibiotic resistance genes were identified using the MEGARes database. Associations between ESBL gene abundance changes and antibiotic exposure were examined using univariate and Inverse Probability of Treatment Weighting linear regression models with covariate balancing propensity scores. RESULTS: Pre-existing gut resistome disruption at the time of HCT showed a stronger correlation with ESBL gene expansion than post-transplant antibiotic exposure. Specifically, patients with greater baseline resistome distance from healthy children showed increased ESBL genes during the neutropenic period. Post-transplant β-lactam exposure (total or ESBL-cleavable) did not correlate with increases in ESBL genes in already-colonized patients. However, aminoglycosides and anaerobic active antibiotics were associated with acquisition of new ESBL organisms during the neutropenic period, while pre-existing microbiome disruption primarily drove selection of resistant bacteria already present. CONCLUSIONS: These findings indicate that antibiotic stewardship before HCT, in addition to reducing the use of anaerobic active antibiotics during early transplant, may be necessary to prevent ESBL-related infections in pediatric transplant recipients. LAY SUMMARY: Infections are the leading cause of death after HCT, and recently the role of the gut microbiome in harboring dangerous bacteria has been highlighted. This study aims to understand multidrug resistant bacteria changes in the gut microbiome early after HCT.