Commercially available tests for determining cefiderocol susceptibility display variable performance in the...

Area of Science:

• Antimicrobial resistance
• Clinical microbiology
• Infectious diseases

Background:

• Cefiderocol is a cephalosporin used for Achromobacter infections.
• Susceptibility testing for cefiderocol presents challenges.
• Standardized testing recommendations vary by pathogen.

Purpose of the Study:

• Evaluate commercial cefiderocol susceptibility tests for Achromobacter.
• Compare diffusion and broth microdilution methods.
• Review existing literature on cefiderocol testing in this genus.

Main Methods:

• Compared diffusion (disks, MIC gradient test strips) and broth microdilution (ComASP™, UMIC®) methods.
• Used 143 Achromobacter strains across 14 species.
• Followed EUCAST guidelines for comparison against BMD reference method.

Main Results:

• No tested method achieved acceptable essential agreement.
• MIC gradient test strips showed the lowest essential agreement.
• UMIC® and ComASP™ failed to identify resistant strains, unlike diffusion methods.

Conclusions:

• MIC gradient test strips are not recommended for Achromobacter.
• Disk diffusion can screen for susceptible strains (≥30 mm zone).
• UMIC® and ComASP™ require combination with disk diffusion for resistance detection.