Objective: Our objective was to investigate activity of cefiderocol against 115 clinical isolates of Enterobacteriaceae including ESBL-producing and carbapenem-resistant strains and compare cefiderocol susceptibility rates between different subsets of bacteria.

Methods: A total of 115 isolates comprising 60 ESBL-producing, carbapenem-susceptible isolates (30 Klebsiella pneumoniae, 30 Escherichia coli) and 55 carbapenem-resistant isolates (40 K. pneumoniae, 15 E. coli) were included in the study. Susceptibility testing for cefiderocol was performed using disk diffusion test. Inhibition zone diameters were interpreted according to EUCAST and CLSI criteria. Pearson Chi-Square test or Fisher’s Exact test, where appropriate, was used to compare cefiderocol susceptibility rates between different subsets of bacteria.

Results: Cefiderocol susceptibility rate among ESBL-producing K. pneumoniae and ESBL-producing E. coli was same (86.7%) according to EUCAST criteria. Cefiderocol susceptibility rates in carbapenem-resistant isolates (74.5% according to EUCAST, 96.4% according to CLSI criteria) were lower than those observed for ESBL-producing isolates (86.7% according to EUCAST, 98.3% according to CLSI criteria), but differences were not statistically significant. Cefiderocol susceptibility rate was 73.3% among OXA-48-producing carbapenem-resistant E. coli isolates and was 96.2% among OXA-48-producing K. pneumoniae isolates according to EUCAST criteria. Cefiderocol susceptibility rate among NDM-producing isolates (45.5% according to EUCAST criteria) were significantly lower than that observed for OXA-48-producing isolates (87.8% according to EUCAST criteria) (p=0.006).

Conclusions: Cefiderocol demonstrated high activity against ESBL-producing K. pneumoniae, ESBL-producing E. coli and OXA-48 carbapenemase-producing K. pneumoniae isolates in our study according to both EUCAST and CLSI criteria. Cefiderocol may be an option for treatment of infections caused by these bacteria.