Characteristics and Resistance Patterns of Gram-Negative Bacterial Isolates to Third-Generation Cephalosporins in Oncology ICU Patients: A Ten-Year Retrospective Analysis

Third-generation cephalosporin (3GC) resistance threatens empirical therapy in vulnerable critically ill patients. We conducted a decade-long single-center retrospective study of 3528 Gram-negative isolates from 1946 adult and pediatric oncology intensive care unit (ICU) patients between 2015 and 2024 at King Hussein Cancer Center. This study aims to characterize 3GS resistance in oncology ICU patients. The 3GC resistance was 59.2% among Enterobacterales and other fermenting organisms (evaluated against the full three-agent panel) and 67.2%among non-fermenters (Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia; evaluated against a narrower, organism-appropriate agent subset); these two estimates are not directly comparable given the differing susceptibility panels tested. Resistance was highest among the Acinetobacter calcoaceticus-baumannii complex (96.9%), followed by Escherichia coli (70.5%), Enterobacter cloacae (65.5%), and Klebsiella pneumoniae (59.6%). In unadjusted patient-level analyses, resistance was significantly higher among patients with hematological malignancy than solid tumors (73.1% vs. 57.8%; OR 1.98, 95% CI 1.59–2.48; p < 0.001) and among pediatric versus adult ICU isolates (70.8% vs. 60.9%; OR 1.55, 95% CI 1.11–2.18; p = 0.010). Seven-day mortality did not differ by resistance status (44.1% vs. 41.6%; unadjusted OR 1.11, 95% CI 0.92–1.33). The 3GC resistance varies by organism, malignancy type and ICU population in unadjusted analyses, supporting population-specific antibiograms and stronger stewardship.