Real-World Use of Cefiderocol for Multidrug-Resistant Gram-Negative Infections in Critically Ill ICU Patients: A Single-Center Case Series.

BACKGROUND/OBJECTIVES: Carbapenem-resistant Gram-negative (CR-GN) infections are associated with high mortality in intensive care units (ICUs), with limited therapeutic options. We aimed to evaluate microbiological and clinical outcomes associated with cefiderocol in critically ill patients with multidrug-resistant (MDR) Gram-negative infections. METHODS: This retrospective, single-center case series included 25 critically ill patients with carbapenem-resistant or multidrug-resistant Gram-negative infections treated with cefiderocol between May 2024 and October 2025 in a mixed ICU of a tertiary hospital in Romania. Microbiological cure was defined as eradication of the designated target pathogen at the end of therapy. Clinical evolution was assessed using the Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores, as well as inflammatory biomarkers including white blood cell count (WBC), C-reactive protein (CRP), and procalcitonin (PCT). RESULTS: Klebsiella pneumoniae was the predominant pathogen, identified in 23 of 25 patients (92%), followed by Acinetobacter baumannii (11/25, 44%) and Pseudomonas aeruginosa (6/25, 24%). As multiple pathogens were co-isolated in 16 patients (64%), percentages exceed 100% and are reported as proportions of patients rather than of total isolates. Microbiological cure was achieved in 68% of patients. Mortality was markedly higher in patients without microbiological eradication (88% vs. 35%). Higher baseline APACHE II (HR 1.18, 95% CI 1.02-1.37) and SOFA scores (HR 1.33, 95% CI 1.07-1.65) were associated with increased mortality. Early initiation of cefiderocol (≤10 days from ICU admission) was associated with improved microbiological and clinical outcomes compared to delayed treatment. Reductions in severity scores and inflammatory markers, including C-reactive protein (CRP) and procalcitonin (PCT), were observed during therapy. Pathogen type and combination therapy were not clearly associated with outcomes in this cohort. CONCLUSIONS: Cefiderocol was observed in association with clinically relevant rates of microbiological eradication and improvements in clinical parameters in critically ill patients with MDR Gram-negative infections. Outcomes appeared to be primarily determined by baseline disease severity, while earlier initiation of therapy was associated with more favourable microbiological and clinical outcomes, although causality cannot be established given the observational design and absence of a comparator group. These findings are hypothesis-generating and supportive of a potential role for cefiderocol as a salvage option in high-risk ICU populations, pending validation in larger, prospective, controlled studies.