2745. In-Vitro Activity of Cefiderocol Against Multidrug Resistant Strains of P. aeruginosa DTR, A. baumannii complex DTR, A. xylosoxidans MDR, S. maltophilia MDR & B. cepacia complex, by Iron-Depleted Broth Microdilution

BACKGROUND: The emergence of multidrug-resistant (MDR) & difficult-to-treat (DTR) non-fermenter (NF) organisms poses a critical challenge for antimicrobial therapy, threatening the efficacy of existing antimicrobial and contributing to an increasing worldwide mortality rate. MDR NFs are among the most challenging organisms isolated in the clinical laboratory. Cefiderocol (CFD), a novel siderophore cephalosporin, offers an interesting approach by exploiting the bacteria's iron-acquisition system and its intrinsic stability against multiple classes of β-lactamases. In this descriptive abstract, we present the in-vitro activity of cefiderocol against multiple strains of NF organisms. Tab.1 [Figure: see text] Cefiderocol MIC distribtion for MDR non-fermenters. Dec. 2022 to April 2023 METHODS: MIC values by iron-depleted broth microdilution (Liofilchem ComASP®) were collected and distributed by organism from December 2022 up to April 2023 at AdventHealth Orlando Microbiology Department. P. aeruginosa DTR (n=88), A. baumannii cpx DTR (n=38), A. xylosoxidans MDR (n=153), S. maltophilia MDR (n=84) & B. cepacia cpx (n=11). P. aeruginosa DTR is defined as an isolate intermediate (I) or resistant (R) to all tested antimicrobials except aminoglycosides. A. baumannii DTR as an isolate I or R to ampicillin/sulbactam and meropenem and one more active agent. A. xylosoxidans MDR as an isolate I or R to one agent in at least three active antimicrobial classes & S. maltophilia MDR as an isolate I or R to trimethoprim/sulfamethoxazole. RESULTS: The average, mode, median and range MIC (µg/mL) were calculated for each organism. P. aeruginosa DTR: 3.55, 0.25, 0.5, 0.06-128; A. baumannii DTR: 7.66, 0.5, 0.5, 0.12-128; A. xylosoxidans MDR: 3.66, 0.25, 0.25, 0.06-128; S. maltophilia MDR 0.37, 0.25, 0.25, 0.06-2; B. cepacia cpx: 11.77, 0.06, 0.06, 0.06-128. CONCLUSION: Using the P. aeruginosa susceptible CLSI BP (< =4 µg/mL) as a reference for P. aeruginosa DTR, A. xylosoxidans MDR & B. cepacia cpx, 96.6%, 97.39% & 90.9% respectively have an MIC value in the susceptible BP. 76.3% of A. baumannii DTR have an MIC < =4 µg/mL (susceptible BP) and 97.6% of S. maltophilia MDR have a susceptible CLSI BP < =1 µg/mL. Although clinical outcome data is needed, cefiderocol demonstrated a significant potency against the most resistant NF strains and may represent a significant therapeutic option for difficult to treat isolates. DISCLOSURES: Jose Alexander, MD, D(ABMM), FCCM, CIC, SM/MB(ASCP), BCMAS, Shionogi: Advisor/Consultant|Shionogi: Honoraria