Preliminary results of antibacterial therapy escalation strategy in the early posttransplant period in patients after allogeneic hematopoietic stem cell transplantation. A retrospective study from a single center

Background. Infectious complications remain a leading cause of early transplant-related mortality following allogeneic hematopoietic stem cell transplantation (allo-HSCT), particularly during the period of febrile neutropenia. Despite advances in transplantation techniques and supportive care, the optimal strategy for empirical antibacterial therapy in this high-risk population remains controversial, especially in resource-limited settings.

Aim. To evaluate the incidence and spectrum of infectious complications, their impact on early mortality after allo-HSCT, and to assess the effectiveness and safety of an escalation-based empirical antibacterial therapy strategy in a single transplantation center with limited resources.

Materials and methods. A single-center retrospective study included 45 adult patients who underwent allo-HSCT between 2023 and 2025 (acute myeloid leukemia – 21, acute lymphoblastic leukemia – 15, aplastic anemia – 8, myelodysplastic syndrome – 1). All patients received a uniform conditioning regimen based on fludarabine and melphalan (FluMel140). The incidence of febrile neutropenia, bloodstream infections, sepsis and septic shock, intensive care unit admission, and early mortality (≤30 days post-transplant) were analyzed. All patients received empirical antibacterial therapy following an escalation strategy. Microbiological identification was performed using VITEK 2 COMPACT and VITEK MS PRIME systems.

Results. Febrile neutropenia occurred in 100 % of patients. Recurrent febrile neutropenia was observed in 44 % of cases, requiring escalation of antibacterial therapy to carbapenems. Microbiologically documented bloodstream infections were identified in 13 % of patients. Sepsis with subsequent septic shock developed in 22 % of patients and was associated with 100 % mortality in this subgroup. Gram-negative pathogens predominated among fatal infections, with Klebsiella pneumoniae and Pseudomonas aeruginosa being the most frequently identified organisms. Late colonization with Klebsiella pneumoniae was observed in all patients who died from infectious complications.

Conclusion. Infectious complications remain the principal cause of early mortality after allo-HSCT. An escalation-based empirical antibacterial therapy strategy represents a feasible and reproducible approach in the majority of allo-HSCT recipients. However, in patients with a high infectious risk profile and colonization with multidrug-resistant organisms, this strategy may be insufficient. The obtained results highlight the need for individualized empirical therapy, enhanced microbiological monitoring, and optimization of conditioning regimens, particularly in resource-limited transplant centers.