In Vitro Antimicrobial Activity of the Siderophore Cephalosporin Cefiderocol against <i>Acinetobacter baumannii</i> Strains Recovered from Clinical Samples

• Main Authors: Davide Carcione (Author), Claudia Siracusa (Author), Adela Sulejmani (Author), Roberta Migliavacca (Author), Alessandra Mercato (Author), Aurora Piazza (Author), Luigi Principe (Author), Nicola Clementi (Author), Nicasio Mancini (Author), Valerio Leoni (Author), Jari Intra (Author)
• Format: Book
• Published: MDPI AG, 2021-10-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.3390/antibiotics10111309; 2079-6382
• Keywords: antimicrobial resistance; nosocomial infection; cefiderocol; siderophore-cephalosporin; <i>Acinetobacter baumannii</i>; Therapeutics. Pharmacology; RM1-950
• Source: Antibiotics, Vol 10, Iss 11, p 1309 (2021)

Background: Cefiderocol is a siderophore cephalosporin that exhibits antimicrobial activity against most multi-drug resistant Gram-negative bacteria, including Enterobacterales, <i>Pseudomonas aeruginosa</i>, <i>Acinetobacter baumannii</i>, and <i>Stenotrophomonas maltophilia</i>. Methods: A total of 20 multidrug-resistant <i>A. baumannii</i> strains were isolated from 2020 to 2021, molecularly characterized and tested to assess the in vitro antibacterial activity of cefiderocol. Thirteen strains were carbapenem-hydrolysing oxacillinase OXA-23-like producers, while seven were non-OXA-23-like producers. Minimum inhibitory concentrations (MICs) were determined by broth microdilution, considered as the gold standard method. Disk diffusion test was also carried out using iron-depleted CAMHB plates for cefiderocol. Results: Cefiderocol MICs ranged from 0.5 to 1 mg/L for OXA-23-like non-producing <i>A. baumannii</i> strains and from 0.25 to >32 mg/L for OXA-23-like producers, using the broth microdilution method. Cefiderocol MIC₉₀ was 8 mg/L. Diameter of inhibition zone of cefiderocol ranged from 18 to 25 mm for OXA-23-like non-producers and from 15 to 36 mm for OXA-23-like producers, using the diffusion disk method. A large variability and a low reproducibility were observed during the determination of diameter inhibition zone. Molecular characterization showed that all isolates presented the ISAba1 genetic element upstream the <i>bla</i>OXA-51. Among OXA-23-like non-producers, four were <i>bla</i>OXA-58 positive and two were negative for all the resistance determinants analyzed. Conclusions: Cefiderocol showed in vitro antimicrobial activity against both carbapenem-susceptible and non-susceptible <i>A. baumannii</i> strains, although some OXA-23-like producers were resistant. Further clinical studies are needed to consolidate the role of cefiderocol as an antibiotic against MDR <i>A. baumannii</i>.