Importance of Microbiological Surveillance in Identifying Colonization by Multidrug-Resistant Bacteria in Hospitalized Onco-Hematological Patients and Hematopoietic Stem Cell Transplant Recipients

Onco-hematological and transplant patients are at high risk of infection by multidrug-resistant bacteria, with high mortality. Colonization by carbapenem-resistant Enterobacterales is a relevant risk factor, especially during neutropenia. Microbiological surveillance helps guide empiric antimicrobial therapy and enables early implementation of precaution measures. This study aimed to evaluate the importance of admission and point-prevalence surveillance cultures in detecting colonization by multidrug-resistant bacteria in hospitalized onco-hematological patients and hematopoietic stem cell transplant (HSCT) recipients. Retrospective study conducted between 01/01/2022 and 12/31/2024 in a tertiary hospital, including all patients admitted to the onco-hematology and HSCT units. Rectal swabs (or perianal swabs in cases of neutropenia) were collected at admission and weekly after 72 hours of hospitalization if the initial swab was negative. Samples were plated on specific media for detection of vancomycin-resistant Enterococcus (VRE), carbapenem-resistant Enterobacterales, and non-fermenting Gram-negative bacilli. Data were extracted from the SCIH electronic database. Colonization prevalence was calculated, the clinical-demographic profile of colonized patients was described, and the incidence of healthcare-associated infection (HAI) and 30-day and in-hospital mortality were assessed. A total of 4,571 samples from 681 patients were included; median age 51 years (2–92), 53.7% male. There were 2,757 (60.3%) admission collections and 1,814 (39.6%) point-prevalence collections. Admission detection: 45 microorganisms (1.6%), with Klebsiella pneumoniae (68.9%), E. coli (15.6%), and other enterobacteria (6.7%). Point-prevalence collections: 51 microorganisms (2.8%), with K. pneumoniae (66.7%), P. aeruginosa (7.8%), and Enterococcus spp. (5.9%). Among positives, 51.1% (admission) and 72.5% (point-prevalence) were HSCT. HAI occurred in 14 (14.6%) colonized patients. Six patients died within 30 days of colonization, five (83.3%) from point-prevalence collections. Point-prevalence collections showed higher positivity and association with HAI than admission collections. Weekly screening enables early identification of colonization and is valuable for preventing transmission and supporting therapeutic decision-making.