Levofloxacin prophylaxis vs no prophylaxis in neutropenic patients within an endemic country for carbapenem-resistant GNB

: Fluoroquinolone prophylaxis (FQ-P) usefulness in neutropenic patients is controversial. In recent decades, Italian epidemiological data has shown worrisome rates of FQ resistance. A single-center cohort study on 136 autologous stem cell transplantations (ASCTs) and 223 allogeneic hematopoietic stem cell transplantations (allo-HSCTs) was performed from Jan-2018 to Dec-2020. Piperacillin/tazobactam was the first-line therapy for febrile neutropenia (FN). Since Feb-2019, FQ-P was omitted. We evaluated the day +30 post-transplant cumulative incidence function (CIF) of Gram-negative bacteria pre-engraftment blood-stream infections (PE-BSIs) and any changes in antimicrobial resistance, FN and infection-related mortality (IRM). In ASCTs, ≥1 FN episode occurred in 74.3% of transplants, without differences among groups [p=0.66]. CIF of Gram-negative bacteria PE-BSI was 10.1% with a significant difference according to FQ-P [0% (LEVO-group) versus 14.1% (NO-LEVO-group), p=0.016]. CIF of IRM was 0% in both groups. In allo-HSCTs, ≥1 FN episode occurred in 96.4% of transplants, without differences among groups [p=0.72]. CIF of Gram-negative bacteria PE-BSI was 28% and it was significantly higher without FQ-P [14.7% (LEVO-group) versus 34.4% (NO-LEVO-group), p=0.003]. CIF of IRM was 5%, superimposable in both groups [p=0.62]. Comparing antimicrobial resistance among Gram-negative bacteria in the setting of allo-HSCT, in the group without FQ-P a significantly higher proportion of pathogens was susceptible to piperacillin/tazobactam (71% versus 30%, p=0.026), FQ (49% versus 10%, p=0.03) and carbapenems (95% versus 50%, p=0.001). FQ-P discontinuation increased Gram-negative bacteria PE-BSI, but it did not impact IRM, both in ASCT and allo-HSCT setting; importantly, it concurred to decrease significantly antimicrobial resistance in Gram-negative bacteria.