Levofloxacin Prophylaxis in Pediatric and Young Adult Allogeneic Hematopoietic Stem Cell Transplantation Recipients Does not Prevent Infective Complications and Infections-related Deaths

Background: The prophylactic use of quinolones in the setting of allogeneic hematopoietic stem cell transplantation (allo-HCT) is controversial and solid evidence is missing, particularly in children. Methods: In this single-center retrospective study, we compared outcomes in patients receiving (n = 74) or not receiving (n = 70) levofloxacin (LVX) prophylaxis, assessing overall survival, event-free survival, acute graft-versus-host disease (aGvHD) and bloodstream infection incidence, and infection-related mortality. Gut microbiota composition was analyzed in a subgroup using 16S rRNA sequencing of stool samples collected pre-HCT and at engraftment. Results: We analyzed 144 allo-HCT in 143 patients performed for any indication. No differences were found in the 2 groups regarding main HCT outcomes, namely, cumulative incidence of aGvHD (37.9% vs 43.5%; P =. 733), grade III-IV aGvHD (12.2% vs 8.7%; P =. 469), gut aGVHD (12.2% vs 17.5%; P =. 451), bloodstream infections (25.6% vs 34.1%; P =. 236) and death from bacterial infection (9.5% vs 4.3%; P = 0.179). In patients experiencing bacterial infections, those receiving prophylaxis showed higher incidence of quinolone-resistant strains (P =. 001). On a subgroup of 50 patients, we analyzed the gut microbiota composition, showing a lower abundance of Blautia (P =. 015), Enterococcus (P =. 011), and Actinomyces (P =. 07) at neutrophil engraftment in patients receiving LVX prophylaxis. Conclusions: LVX prophylaxis in the setting of allo-HCT does not prevent infective complications and increases the prevalence of antibiotic-resistant strains.