Bloodstream Infections Epidemiology and Clinical Ou0.0003tcomes after one year post Allogeneic Hematogenous Stem Cell Transplantation

Silvia Corcione^1,2Bianca Maria Longo^3*Walter Rugge¹Ilaria De Benedetto¹Tommaso Lupia⁴Nour Shbaklo¹Sofia Zompi⁵Jessica Gill^5,6Antonio Curtoni⁷Roberto Passera¹Alessandro Busca⁵Benedetto Bruno^6,8Francesco Giuseppe De Rosa¹

• ¹Department of Medical Sciences, School of Medicine, University of Turin, Turin, Piedmont, Italy
• ²School of Medicine, Tufts University, Boston, Massachusetts, United States
• ³Cardinal Massaia Asti Hospital, ASTI, Italy
• ⁴Unit of Infectious Diseases, University Hospital Città della Salute e della Scienza di Torino, Torino, Italy
• ⁵Department of Oncology, Stem Cell Transplant Center, Città della Salute e della Scienza Hospital, Turin, Italy
• ⁶Molecular Biotechnology Center, Department of Molecular Biotechnology and Health Sciences, School of Medicine, University of Turin, Torino, Piedmont, Italy
• ⁷Microbiology and Virology Unit, University Hospital of the City of Health and Science of Turin, Turin, Piedmont, Italy
• ⁸Division of Hematology, AOU "Città della Salute e della Scienza di Torino", Turin, Italy

Background: Bloodstream infections (BSIs) are a serious threat for patients undergoing allogenic hematopoietic stem cell transplants (a-HSCT). MDR colonization is highly prevalent among a-HSCT patients, due to drug-induced intestinal dysbiosis. Primary outcome of the study was to assess the epidemiology and risk factors for BSIs in the first year after a-HSCT. Secondary endpoints were to examine the prevalence of MDR bacterial colonization and factors affecting 1-year post-transplant overall survival (OS).In this single-center observational cohort study, all consecutive adult patients undergoing a-HSCT for hematological malignancies between 2012 and 2021 were retrospectively enrolled at the Stem Cell Transplant Center, AOU Città della Salute e della Scienza, Turin (Italy). Cumulative Incidence and risk factors for BSIs were analyzed by Gray and Fine-Gray tests, respectively. OS was evaluated with Kaplan-Meier, while the influence of covariates on OS with Cox regression analysis.Results: 279 patients were enrolled in the study, 43% of which developed BSI within the first-year post-transplant. The median onset of BSIs was 10 days after a-HSCT and Gram-negative bacteria were the most common causative agents (58.3%). 20.8% of patients had a positive rectal swab (RS) for MDR bacteria, with extended-spectrum β-lactamases (ESBLs)-producing Enterobacterales being the most common colonizers (60.3% of positive RS), followed by carbapenem-resistant Enterobacteriaceae (CRE) (29.3%). Multivariate competing risks regression analysis showed that colonisation by MDR bacteria was associated with a higher incidence of BSIs (SDHR 1.49, 95%CI 1.01 -2.20), along with the type of underlying disease (SDHR 0.73, 95%CI 0.58 -0.91), donor type (SDHR 1.62, 95%CI 1.02 -2.58) and an advanced disease status at the time of transplantation (SDHR 1.57, 95%CI 1.05 -2.35). One-year mortality rate was 25.4%. RS colonization was not associated with increased mortality; while BSIs adversely affected OS (SDHR 1.52, 95%CI 1.02-2.26).BSIs are common complications in a-HSCT, with evidence suggesting a negative impact on OS. Although MDR colonization is not independently linked to increased mortality in a-HSCT, it appears to be associated with an elevated risk of subsequent BSI development. These findings underscore the potential value of pretransplant surveillance, contact precautions, and early targeted antimicrobial therapy in colonized patients to help mitigate infection-related morbidity and mortality