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Performance evaluation of the UMIC® Cefiderocol to determine MIC in Gram-negative bacteria
Laurent Dortet1,2,3, Claudia Niccolai4,5, Niels Pfennigwerth6
1Team "Resist", INSERM Unit 1184, Faculty of Medicine, Université Paris-Saclay, Service de Bactériologie-Hygiène, Hôpital Bicêtre, 78 rue du Général Leclerc, 94275, Le Kremlin-Bicêtre, France.
Background:
Cefiderocol is a catechol-substituted cephalosporin with potent in vitro activity against carbapenem-resistant (CR) Gram-negative bacteria (GNB). Cefiderocol susceptibility testing is complex because iron concentrations need to be taken into consideration. Here, we assessed the clinical performance of Bruker's UMIC® Cefiderocol and corresponding iron-depleted CAMHB to determine MIC by broth microdilution (BMD) for clinically relevant GNB.
Methods:
MICs of cefiderocol for 283 GN clinical isolates were determined by BMD using iron-depleted CAMHB. Frozen panels were used as a reference. The concentration range of cefiderocol was 0.03-32 mg/L. The isolates, with different degrees of susceptibility to cefiderocol, included Enterobacterales (n = 180), Pseudomonas aeruginosa (n = 49), Acinetobacter baumannii (n = 44) and Stenotrophomonas maltophilia (n = 10).
Results:
The rates of categorical agreement (CA), essential agreement (EA) and bias were calculated to evaluate the performance of the UMIC® Cefiderocol, as compared with the reference method. Overall, the UMIC® Cefiderocol showed 90.8% EA (95% CI: 86.9%-93.7%) with a bias of -14.5% and a CA of 90.1% (95% CI: 86.1%-93.1%). For Enterobacterales, the UMIC® Cefiderocol showed 91.7% EA (95% CI: 86.7%-94.9%) with a bias of -25.0% and a CA of 87.8% (95% CI: 82.2%-91.8%). For non-fermenters, the UMIC® Cefiderocol showed 89.3% EA (95% CI: 81.9%-93.9%) (not significantly different from 90.0%, Student t-test) with a bias of -3.9% and a CA of 94.2% (95% CI: 87.7%-97.3%).
Conclusions:
UMIC® Cefiderocol is a valid method for the determination of cefiderocol MICs even if higher than expected discrepancies were observed with NDM-producing Enterobacterales, which presented in most cases MIC values close to the breakpoint.
Insights
Bruker
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Resistance
Background:
- Cefiderocol demonstrates potent in vitro activity against carbapenem-resistant Gram-negative bacteria.
- Accurate susceptibility testing for cefiderocol is challenging due to iron concentration variability.
- Assessing the clinical performance of Bruker's UMIC® Cefiderocol assay is crucial for reliable diagnostics.
Purpose of the Study:
- To evaluate the clinical performance of Bruker's UMIC® Cefiderocol assay for determining cefiderocol minimum inhibitory concentrations (MICs).
- To compare the UMIC® Cefiderocol assay results against a reference broth microdilution method using iron-depleted CAMHB.
- To assess the assay's accuracy for clinically relevant Gram-negative bacterial isolates.
Main Methods:
- MICs for 283 Gram-negative clinical isolates were determined using broth microdilution (BMD) with iron-depleted CAMHB.
- Isolates included Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia.
- Performance was evaluated by calculating categorical agreement (CA), essential agreement (EA), and bias against a reference method.
Main Results:
- The UMIC® Cefiderocol assay demonstrated 90.8% essential agreement and 90.1% categorical agreement overall.
- For Enterobacterales, essential agreement was 91.7% and categorical agreement was 87.8%.
- For non-fermenters, essential agreement was 89.3% and categorical agreement was 94.2%.
Conclusions:
- Bruker's UMIC® Cefiderocol assay is a valid method for determining cefiderocol MICs.
- The assay shows good overall performance, with high essential and categorical agreement.
- Discrepancies were noted for NDM-producing Enterobacterales, warranting careful interpretation near the breakpoint.
