P11. Cefiderocol for Gram-negative infections: comparing monotherapy and combination therapy in the multicenter CEFI-BAC study

Real-life data on cefiderocol for Gram-negative infections remain limited. We aimed to evaluate factors associated with mortality in patients treated with cefiderocol either as monotherapy or combination therapy.

A retrospective multicenter study using the CEFI-BAC cohort was conducted across 17 Italian centers on adults treated with cefiderocol (January 2021–February 2023). Data included patient characteristics, infections, prescriptions, end-of-treatment (EOT) outcomes, and mortality (in-hospital/30-days). Statistical comparisons were performed using Chi-square/Fisher’s tests and the Mann-Whitney U test. Factors associated with 30-days mortality were analyzed using multivariate Cox regression.

Among 243 patients, 65% were male (median age 68 years). Major infections included bloodstream infections (61%, 149/243) and nosocomial pneumonia (14%, 34/243) with Acinetobacter baumannii (64%, 157/243), Pseudomonas aeruginosa (17%, 42/243), and Klebsiella spp. (23%, 57/243) as most common pathogens. Median treatment lasted 10 days (IQR 7–15) with five adverse events reported. Clinical cure at EOT was 59% (143/243). EOT mortality for all patients was 22.5% (50/243), and in- hospital mortality was 40.3% (93/243). Cefiderocol was used in combination therapy in 56% of cases (137/243), mainly for severe infections, including polymicrobial infections (34%, 46/243) and septic shock (27%, 37/243) (Table 1). Monotherapy correlated with higher comorbidity burden. EOT mortality was 17% (18/106) for monotherapy and 23% (32/137) for combination therapy, with no significant differences in in-hospital mortality (36.5%, 35/243 versus 42.9%, 58/243; P = 0.320) or hospitalisation length (40 [IQR 24–72] versus 46 days [IQR 25–76]; P = 0.340). Kaplan-Meier analysis confirmed no significant differences in 30-day mortality (Figure 1). Multivariate Cox regression identified advanced age (aHR: 1.25/year, P = 0.038), prior antibiotics (aHR: 4.31–7.50, P < 0.05), concurrent SARS-CoV-2 infection (aHR: 4.40, P < 0.01), and New Delhi Metallo-beta-lactamase NDM-type infection mechanisms (aHR: 6.42, P = 0.001) as significant predictors of 30-days mortality.