Infection-related mortality after hematopoietic stem cell transplantation in a high antimicrobial resistance setting

Infectious complications remain a leading cause of mortality after hematopoietic stem cell transplantation (HSCT). We aimed to describe post-HSCT infections and their impact on survival in a center from a region with high antimicrobial resistance. We included 522 patients with hematological malignancies undergoing HSCT at Koç University Hospital between 2016 and 2024. Bloodstream and opportunistic infections within 100 days were analyzed. Infection-related mortality (IRM) was defined as death primarily attributable to infectious complications. Predictors of 30- and 100-day mortality were assessed using multivariate logistic regression, including demographic and hematologic features, bloodstream infections (BSIs), invasive aspergillosis (IA), and cytomegalovirus reactivation. The most frequent diagnoses were non-Hodgkin lymphoma (36%), multiple myeloma (33%), and Hodgkin lymphoma (11%). Gram-negative bacteria (GNB) accounted for 73% of BSIs; Escherichia coli (31%) and Klebsiella pneumoniae (30%) were most frequent. Carbapenem resistance was highest in Klebsiella pneumoniae (67%), mainly due to OXA-48 carbapenemase (43%). Carbapenem-resistant Klebsiella pneumoniae (CRKP) bacteremia was associated with significantly reduced 100-day survival (log-rank p < 0.001). IA also significantly impaired survival in the overall cohort (log-rank p < 0.001). In the allogeneic subgroup (n = 139), 100-day mortality reached 27%, with IA occurring in 19% and CRKP bacteremia in 17%. At 30 days, 25 patients (5%) had died; 24 of these deaths (96%) were attributed to infections. By day 100, 52 patients (10%) had died, and infections accounted for 42 deaths (80%). In a high antimicrobial resistance setting, CRKP bacteremia and invasive aspergillosis were major determinants of early post-HSCT mortality. These findings highlight the need for optimized empirical therapy, antimicrobial stewardship, and strengthened infection prevention strategies in this vulnerable population. Infection-related mortality accounted for the majority of early deaths after HSCT in this high antimicrobial resistance setting. Carbapenem-resistant Klebsiella pneumoniae bacteremia was an independent predictor of both 30-day and 100-day mortality. Pseudomonas aeruginosa bacteremia and invasive aspergillosis were also associated with significantly reduced survival. The OXA-48 gene was the most common molecular type of Klebsiella pneumoniae. Invasive aspergillosis occurred in 12% of patients—particularly in the allogeneic group—and was strongly associated with prolonged neutropenia and corticosteroid use.