Rapid cefiderocol NP test for detection of cefiderocol susceptibility/resistance in Enterobacterales

J Antimicrob Chemother. 2022 Nov 28;77(12):3456-3461. doi: 10.1093/jac/dkac340.


Background: Cefiderocol is among the latest generation of commercialized antibiotics against a large variety of MDR Gram-negative bacteria including carbapenem-resistant Enterobacterales and non-fermenters such as Pseudomonas aeruginosa and Acinetobacter baumannii. Cefiderocol susceptibility testing, a key element for implementing rapidly a cefiderocol-based treatment, might be still challenging.

Objectives: To develop a rapid culture-based test, Rapid Cefiderocol NP test, for the identification of cefiderocol resistance among MDR Enterobacterales.

Methods: The Rapid Cefiderocol NP test is based on glucose metabolization when bacterial growth occurs and the detection of bacterial growth in the presence of cefiderocol at 64 mg/L using iron-depleted CAMHB. Bacterial growth is visually detectable by a red-to-yellow colour change of red phenol, a pH indicator. A total of 74 clinical enterobacterial isolates from various clinical sources and of worldwide origin, among which 42 isolates were cefiderocol resistant, were used to evaluate the test performance.

Results: The sensitivity and specificity of the test were found to be 98% and 91%, respectively, by comparison with the reference broth microdilution (BMD) method. All positive results were obtained within 3 h after incubation at 35°C ± 2°C, that is a gain of time of ca. 18 h (1 day) compared with currently used techniques for susceptibility testing (BMD method).

Conclusions: This novel test is rapid, highly sensitive, specific, easily interpretable, and easy to implement in routine microbiology laboratories. Such a test may rapidly and accurately provide the information needed for the implementation of adequate cefiderocol-based treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Anti-Bacterial Agents / therapeutic use
  • Cefiderocol
  • Cephalosporins* / pharmacology
  • Cephalosporins* / therapeutic use
  • Drug Resistance, Multiple, Bacterial*
  • Gram-Negative Bacteria
  • Microbial Sensitivity Tests
  • Pseudomonas aeruginosa


  • Cephalosporins
  • Anti-Bacterial Agents