Patients with hematologic diseases colonized by multidrug-resistant (MDR) bacteria have a higher incidence of bloodstream infections and reduced overall survival when colonized by carbapenemase-producing Klebsiella pneumoniae bacteria, according to research published in the journal Transplant Infectious Disease.

Researchers conducted a single-center retrospective cohort study to investigate whether colonization by MDR bacteria negatively impacts clinical outcomes in patients with hematologic diseases after hematopoietic stem cell transplantation (HSCT) and evaluated potential risk factors for death due to bacteremia by the same colonizing agent.

A total of 405 patients underwent a single HSCT procedure due to malignant or nonmalignant hematological diseases at a single tertiary referral care hospital between September 1, 2015, and August 31, 2021. Most patients were adults (58.8%), male (59.8%), and underwent allogeneic transplantation (84.7%).

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Based on surveillance cultures from day D-30 to D+30 of transplantation, 32.6% of patients were colonized by at least 1 MDR bacteria while 67.4% were noncolonized.

The study found that colonization by MDR bacteria increased the cumulative incidence of positive blood cultures caused by any given pathogen from 20.5% (noncolonized) to 36.4% (P =.0002) and also specifically by MDR bacteria, with the most pronounced effect caused by carbapenemase-producing K. pneumoniae from 22.4% to 56.4% (P <.0001).

The researchers also demonstrated that patients colonized with carbapenemase-producing K. pneumoniae had increased overall mortality (hazard ratio [HR], 4.07; 95% CI, 1.85-8.91; P =.0005) and experienced prolonged hospital length of stay in the context of autologous transplantation (median, 80 vs 28 discharged days; P =.0137) compared to patients not colonized by that agent.  

Multivariate analysis revealed risk factors for death due to bacteremia by the same colonizing agent were colonization by carbapenemase-producing K. pneumoniae (HR, 4.63, 95% CI, 1.54-13.90; P =.0063) and use of high-dose total body irradiation in conditioning (HR, 3.02; 95% CI, 1.05-8.65; P =.0400).

“In conclusion, pre-HSCT to D+30 colonization of hematological patients by MDR bacteria results in higher incidences of bloodstream infections, and when it occurs by carbapenem-resistant K. pneumoniae, it also negatively impacts transplantation clinical outcomes,” wrote the study authors. “This study emphasizes the importance of preventive methods for control of MDR colonizing bacteria and of rapid laboratory detection of colonization and infection, as well as highlights the requirement for appropriate antimicrobial empirical treatment in colonized hematological patients with post-HSCT manifestations of bloodstream infections.”

Limitations of the study included the retrospective design, including potentially incomplete or inaccurate data and unmeasured confounding factors, and use of different antimicrobial protocols and treatments over time.


Santos ES, Lima ACM, Breda GL, et al. Colonization by multidrug-resistant bacteria in hematological patients undergoing hematopoietic stem cell transplantation and clinical outcomes: A single-center retrospective cohort study. Transpl Infect Dis. Published online August 10, 2023; e14119. doi:10.1111/tid.14119