Bacterial Bloodstream Infections After Hematopoietic Cell Transplantation With Post-Transplant Cyclophosphamide.

Bacterial bloodstream infections (BSI) are an important contributor to morbidity and mortality after hematopoietic cell transplant (HCT). Its specific characteristics with the use of post-transplant cyclophosphamide (PTCy) remain poorly defined, particularly in the HLA-matched setting. The objectives were to evaluate the characteristics, incidence, risk factors, and clinical impact of bacterial BSI in patients with hematologic malignancies undergoing HCT from matched related (MSD), matched unrelated (MUD), and haploidentical donors using PTCy-based graft-versus-host disease (GVHD) prophylaxis. We conducted a retrospective single-center analysis of bacterial BSI in 456 patients undergoing HCT. Quinolone prophylaxis was administered during neutropenia, and screening for bacterial colonization was performed during hospitalization, regardless of transplant timing. Median age at HCT was 55 yr, with 63% diagnosed with acute leukemia. HCT was performed with MSD in 40%, MUD in 34% and haploidentical donors in 26%. A total of 159 bacterial BSI episodes were observed in 128 patients. The cumulative incidence of first BSI was 28% at 2 yr at a median time of 11 d (range, 1-694). Regarding timelines, 60% of episode occurred until d +30, 19% between d +31 and +100, 14% between d +100 and one year, and 7% beyond the first year. There was a predominance of gram-negative bacterial infections, particularly in haploidentical HCT during the first 30 d. Multidrug resistance criteria was met in 55% of gram-negative and 47% of gram-positive bacteria. Haploidentical donors were independently associated with early BSI, while grade II-IV acute GVHD increased the risk after d +30. BSI-related mortality accounted for 9% of deaths, and late-onset BSI was associated with inferior OS. In conclusion, bacterial BSI affects over one-fourth of PTCy-based HCT recipients, particularly in the early post-transplant period, with a predominance of gram-negative microorganisms. Haploidentical donors and acute GVHD were independent risk factors for BSI, and late-onset BSI was associated with worse OS.