The impact of infections on survival in patients after hematopoietic stem cell transplantation

Introduction: Infectious complications in hematopoietic stem cell transplantation (HSCT) are significant causes of mortality. We aimed to describe postHSCT infections and their impact on survival in a center with high antimicrobial resistance rates. Method: We reviewed patients over the age of 18 with hematological malignancies who had HSCT at Koç University Hospital between 2016 and 2024. Demographic and clinical features were noted. The bacterial agents and resistance rates in bloodstream infections (BSI) during the first 100 days were determined. Univariate and multivariate analysis were performed for increasing factors of invasive aspergillosis (IA). Risk factors for Cytomegalovirus (CMV) reactivation were analyzed in the allogenic HSCT group. Independent variables identified as potential predictors of mortality included gender, age, hematologic diagnosis, relapsed/refractory (R/R) disease, type and number of transplants, BSI, IA and CMV. A multivariate logistic regression analysis was conducted, with 30-day and 100-day mortality as the endpoints, and backward selection was performed in logistic regression. Results: The diagnoses of 522 patients were grouped as non-Hodgkin lymphoma (%36), multiple myeloma (%33), Hodgkin lymphoma (%11), acute myeloid leukemia (%9.5), acute lymphoblastic leukemia (%5) and myelodysplastic syndrome (%2). Gram-negative (GN) bacteremia (%73) was more frequently isolated compared to Gram-positive bacteremia (%24%). Among GN bacteremia cases, Escherichia coli (%32) and Klebsiella pneumoniae (%30) were the most common pathogens. Phenotypic carbapenem resistance was most frequently observed in Klebsiella pneumoniae (%71), with OXA-48 carbapenemase positivity (%43) being the most common resistance mechanism. Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa bacteremia were found to increase 30-day mortality by 3.6-7.6 times. Among bacterial pathogens, Klebsiella pneumoniae bacteremia was a significant factor for both 30-day and 100-day mortality. IA was diagnosed in 19% of allogeneic and 10% of autologous transplant recipients. IA was identified as an independent predictor of increased mortality. Risk factors for IA were delayed neutrophil engraftment and systemic steroid use. Other infections, including CMV, had no significant impact on mortality. The overall mortality rates were 5% at 30 days and 10% at 100 days. Conclusion: Infections complications of HSCT have adverse effect on survival. The primary causes of infection-related mortality were Klebsiella pneumoniae bacteremia with high carbapenem resistance and invasive aspergillosis. GN bacteremia significantly increased early mortality within the first 30 days. Although Escherichia coli was more frequently isolated, its low carbapenem resistance had been associated with better post-engraftment survival rates. In contrast, due to restricted therapeutic options, Klebsiella pneumoniae bacteremia with carbapenem resistance increased mortality at both 30 and 100 days.Other bacterial, fungal, and viral infections did not have a direct impact on survival. Effective antimicrobial stewardship and infection control measures are crucial for improving the survival of HSCT patients Key words: Mortality, bone marrow transplant, blood stream infections