Abstract
BACKGROUND: Patients with hematologic malignancies are highly vulnerable to Gram-negative bacterial bloodstream infections (GNB-BSIs) due to underlying disease-related immunosuppression, intensive chemotherapy, and repeated invasive interventions, rendering these infections a significant cause of morbidity and mortality in this population. This study aimed to evaluate the epidemiological, clinical, and microbiological features of GNB-BSIs in hospitalized patients with hematologic malignancies, and to compare clinical and microbiological factors between survivors and non-survivors. METHODS: We conducted a retrospective cohort study in a tertiary university hospital hematology ward in Türkiye, including adult patients diagnosed with BSIs due to Gram-negative bacteria between January 2005 and December 2024. Demographic characteristics, microbiological profiles, antimicrobial resistance rates, and clinical outcomes were analyzed. We compared survivors and non-survivors to determine differences in clinical and microbiological characteristics. RESULTS: A total of 321 patients with hematologic malignancies experienced 441 episodes of GNB-BSIs. The median age was 46 years, and 59% of them were male. The most frequently isolated pathogen was Escherichia coli (53.3%), followed by Klebsiella spp. (20.6%) and Pseudomonas spp. (7.5%). Extended-spectrum β-lactamase-producing/third-generation cephalosporin-resistant (ESBL/3GCR) and carbapenem-resistant isolates were observed in 21.1% and 13.3% of isolates, respectively. The overall mortality rate was 26.5%. ICU admission, multidrug resistance, and persistent bacteremia were observed more often among non-survivors. Additionally, prolonged fever duration (median 8 vs. 3 days, p < 0.0001), elevated CRP (p = 0.001), and higher procalcitonin levels (p = 0.046) were detected in non-survivors. CONCLUSIONS: In patients with hematologic malignancies, E. coli and Klebsiella spp. remain the predominant pathogens causing bloodstream infections, while persistent bacteremia, ESBL/3GCR, and carbapenem resistance are associated with higher mortality. Notably, carbapenem resistance showed a temporal increase over the study period, underscoring the need for continuous surveillance and timely adaptation of empirical treatment strategies.