Evolution of β-lactamase-mediated cefiderocol resistance

Background Cefiderocol is a novel siderophore beta-lactam with improved hydrolytic stability toward beta-lactamases, including carbapenemases, achieved by combining structural moieties of two clinically efficient cephalosporins, ceftazidime and cefepime. Consequently, cefiderocol represents a treatment alternative for infections caused by MDR Gram-negatives. Objectives To study the role of cefiderocol on resistance development and on the evolution of beta-lactamases from all Ambler classes, including KPC-2, CTX-M-15, NDM-1, CMY-2 and OXA-48. Methods Directed evolution, using error-prone PCR followed by selective plating, was utilized to investigate how the production and the evolution of different beta-lactamases cause changes in cefiderocol susceptibility determined using microbroth dilution assays (MIC and IC50). Results We found that the expression of bla(OXA-48) did not affect cefiderocol susceptibility. On the contrary, the expression of bla(KPC-2), bla(CMY-2), bla(CTX-M-15) and bla(NDM-1) substantially reduced cefiderocol susceptibility by 4-, 16-, 8- and 32-fold, respectively. Further, directed evolution on these enzymes showed that, with the acquisition of only 1-2 non-synonymous mutations, all beta-lactamases were evolvable to further cefiderocol resistance by 2- (NDM-1, CTX-M-15), 4- (CMY-2), 8- (OXA-48) and 16-fold (KPC-2). Cefiderocol resistance development was often associated with collateral susceptibility changes including increased resistance to ceftazidime and ceftazidime/avibactam as well as functional trade-offs against different beta-lactam drugs. Conclusions The expression of contemporary beta-lactamase genes can potentially contribute to cefiderocol resistance development and the acquisition of mutations in these genes results in enzymes adapting to increasing cefiderocol concentrations. Resistance development caused clinically important cross-resistance, especially against ceftazidime and ceftazidime/avibactam.

Automated summary

This study investigated the impact of cefiderocol on resistance development and the evolution of beta-lactamases from different Ambler classes. The expression of bla(KPC-2), bla(CMY-2), bla(CTX-M-15), and bla(NDM-1) significantly reduced cefiderocol susceptibility, while mutations in these enzymes further increased cefiderocol resistance. Resistance development also led to collateral changes in sensitivity to other beta-lactam drugs and functional trade-offs.