Performance of the Disc Diffusion Method, MTS Gradient Tests and Two Commercially Available Microdilution Tests for the Determination of Cefiderocol Susceptibility in Acinetobacter spp

Katy Jeannot; Susie Gaillot; Pauline Triponney; Sylvain Portets; Valentin Pourchet; Damien Fournier; Anaïs Potron

doi:10.3390/microorganisms11081971

Performance of the Disc Diffusion Method, MTS Gradient Tests and Two Commercially Available Microdilution Tests for the Determination of Cefiderocol Susceptibility in Acinetobacter spp

Microorganisms. 2023 Jul 31;11(8):1971. doi: 10.3390/microorganisms11081971.

Authors

Katy Jeannot^{1

2

3}, Susie Gaillot³, Pauline Triponney², Sylvain Portets¹, Valentin Pourchet¹, Damien Fournier^{1

2}, Anaïs Potron^{1

2

3}

Affiliations

¹ Laboratoire de Bactériologie, CHU de Besançon, F-25000 Besançon, France.
² Centre National de Référence de la Résistance aux Antibiotiques, Laboratoire Associé, Centre Hospitalier Universitaire de Besançon, F-25000 Besançon, France.
³ CNRS, UMR 6249, Chrono-Environnement, Université de Franche-Comté, F-25000 Besançon, France.

Abstract

Cefiderocol is a siderophore-conjugated cephalosporin with potent activity against multidrug-resistant Gram-negative pathogens including Acinetobacter baumannii. The aim of this study was to evaluate cefiderocol testing methods on a relevant collection of 97 Acinetobacter spp. isolates. Commercialized broth microdilution methods (ComASP^®, Liofilchem and UMIC^®, Bruker), MIC test strips (Liofilchem) and disc diffusion using discs of three different brands (Mast Diagnostic, Liofilchem and Oxoid-Thermo Fisher Scientific) were compared with the broth microdilution reference method. None of the methods tested fulfilled acceptable criteria (essential agreement [EA] ≥ 90%; bias = ±30%) but both BMD methods achieved acceptable categorical agreement rates (CA = 95.9% [93/97, 95% CI 89.9-98.4] and CA = 93.8% [91/97, 95% CI 87.2-97.1] for ComASP^® and UMIC^®, respectively) and bias < 30% (-7.2% and -25.2% for ComASP^® and UMIC^®, respectively). The use of MIC gradient testing is strongly discouraged due to misclassification of 55% (n = 23/42) of resistant strains. Finally, the disc diffusion method could be used to rapidly screen for susceptible strains by setting a critical diameter of 22 mm.

Keywords: Acinetobacter spp.; cefiderocol; susceptibility testing.

Grants and funding

This work was co-funded by the French Ministry of Health though the Santé Publique France agency and Shionogi & CO., Ltd., Osaka Japan. The funders had neither a specific role in study design, collection of strains, nor in writing of the paper.