Gram-negative bacterial bloodstream infections in cancer patients: a study of epidemiological trends and antibiotic susceptibility

PURPOSE: The primary aim of this study was to determine the epidemiological characteristics of Gram-negative bloodstream infections (BSIs) and the susceptibility profiles of the causative microorganisms in hospitalized patients with hematological and oncological malignancies. METHODS: This retrospective observational study investigated Gram-negative BSIs in patients over the age of 18 with a diagnosis of malignancy admitted to the hematology and oncology departments of Ankara Bilkent City Hospital between June 1, 2019, and September 1, 2023. Demographic data, disease activation status (new diagnosis, remission and relapse/refractory disease), causative Gram-negative microorganisms, and antibiotic susceptibilities were recorded. RESULTS: A total of 435 patients with 569 Gram-negative bacteremia were included. The median age of the patients was 56 years (range: 18-90 years), and 60.7% were male. Among the BSI episodes, 11.1% were catheter related. The most common Gram-negative pathogens were E. coli (40.6%), Klebsiella spp. (28.8%), and Pseudomonas spp. (9.1%). Of all isolates, 47.7% were multidrug-resistant (MDR), and 26.7% produced extended-spectrum beta-lactamase (ESBL). The rates of ESBL resistance were 40.3% and 28.7% for E. coli and Klebsiella spp., respectively, whereas the carbapenem resistance rates were 9.1% and 27.4%, respectively. Meropenem susceptibility rates were 93.4% for E. coli, 79.1% for Klebsiella spp., and 72.9% for Pseudomonas spp. MDR was most frequent in Acinetobacter spp. (56.5%) and Klebsiella spp. (56.1%), with the highest carbapenem resistance in Acinetobacter spp. (52.2%). CONCLUSION: This study highlights the high prevalence of MDR Gram-negative pathogens, limiting options for effective empirical therapy. The elevated rates of ESBL production, and carbapenem resistance are concerning and underscore the need for strengthened antimicrobial stewardship, updated guidelines, and new treatment options for managing Gram-negative BSIs.