Revisiting fluoroquinolone prophylaxis in haematological malignancies and hematopoietic cell transplantation: A decade of evidence and gaps in understanding the impact of gut colonization with fluoroquinolone-resistant Enterobacterales.

OBJECTIVE

Rising antimicrobial resistance necessitates reevaluation of fluoroquinolone (FQ) prophylaxis (FQP) in patients with hematologic malignancies undergoing intensive chemotherapy or hematopoietic cell transplantation (HCT). This review evaluated the clinical efficacy of FQP and the modifying effect of gut colonization with FQ-resistant Enterobacterales (FQRE).

METHODS

A structured narrative review of studies published between 2015 and 2025 was conducted. Studies comparing FQP with no prophylaxis and studies evaluating outcomes according to baseline colonization with FQRE were reviewed. Clinical outcomes included febrile neutropenia, bloodstream infection, Gram-negative bloodstream infection, pneumonia, Clostridioides difficile-associated diarrhea, mortality, and resistance patterns in breakthrough infections.

RESULTS

FQP consistently reduced febrile neutropenia and bloodstream infections, particularly in autologous HCT and selected chemotherapy cohorts. However, its benefit was context-dependent, with diminished or absent effects in allogeneic HCT and in settings with higher background FQ resistance (≥30%). Breakthrough infections during prophylaxis were predominantly caused by FQ-resistant organisms, reflecting strong selective pressure. Baseline colonization with FQRE further increased the risk of bloodstream infection and reduced the likelihood of benefit from prophylaxis. Mortality was not significantly affected across populations. Available microbiome data suggest that FQP exerts a selective effect on Gram-negative gut colonization rather than causing broad disruption of microbial diversity.

CONCLUSIONS

The effectiveness of FQP is strongly influenced by resistance epidemiology and colonization status. These findings support a shift toward more individualized, resistance-informed prophylaxis strategies within antimicrobial stewardship frameworks.