The aim of this study is to clarify the characteristics of gram-negative bacteremia (GNB), including extended-spectrum β-lactamase (ESBL)-producing pathogens, among allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients on levofloxacin (LVFX) prophylaxis. A retrospective analysis on GNB at the first episode of febrile neutropenia (FN) was conducted among allo-HSCT recipients (age ≥ 20 years) on 500 mg/day of oral LVFX prophylaxis. Epidemiological and microbiological features of GNB were investigated and compared between the inappropriate and appropriate empiric therapy groups. In total, FN occurred in 414 allo-HSCT cases, and bacteremia at the first episode of FN occurred in 169 cases. Overall, 29 GNB cases were documented, and the causative organisms identified were Escherichia coli in 21 cases (including 10 ESBLs), Klebsiella pneumoniae in 2, Pseudomonas aeruginosa in 2, and other in 4. The crude 30-day mortality rate was not significantly different among cases of GNB (6.9%), gram-positive bacteremia (GPB) (7.1%), or non-bacteremia (5.4%; P = 0.78). Cefepime (CFPM) was administered in all cases in the inappropriate empiric therapy group, and all causative organisms were ESBL-producing E. coli (ESBL-EC). All patients in the inappropriate empiric therapy group had a low Pitt bacteremia score (≤ 2). Thirty-day mortality did not differ significantly between the inappropriate and appropriate empiric therapy groups (1/10 vs. 1/15, P = 0.61). In conclusion, GNB was not a significant cause of death. In LVFX breakthrough ESBL-EC bacteremia among allo-HSCT recipients, the administration of CFPM as empiric therapy did not lead to significantly poor prognosis. Empiric CFPM administration might be an acceptable strategy.
Keywords: Allogeneic hematopoietic stem cell transplantation; Extended-spectrum β-lactamase-producing E. coli; Febrile neutropenia; Gram-negative bacteremia; Levofloxacin prophylaxis.