Evolution of β-lactamase mediated cefiderocol resistance

ABSTRACT Cefiderocol is a novel siderophore β-lactam with improved hydrolytic stability toward β-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 multi-drug resistant Gram-negatives. Using directed evolution on a wide variety of different β-lactamases, such as KPC-2 and CTX-M-15 (Ambler class A), NDM-1 (class B), CMY-2 (class C) and OXA-48 (class D), we studied the role of cefiderocol during β-lactamase-mediated resistance development. First, we investigated how the expression of different β-lactamases causes changes in cefiderocol susceptibility. In a low-copy number vector, we found that OXA-48 and KPC-2 conferred non or marginal decreases in cefiderocol susceptibility, respectively. On the contrary, CMY-2, CTX-M-15 and NDM-1 substantially decreased cefiderocol susceptibility by 16-, 8- and 32-fold, respectively. Second, we determined the evolutionary potential of these enzymes to adapt to increasing concentrations of cefiderocol. Our data show that with the acquisition of only 1 to 2 mutations, all β-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 β-lactam drugs. Taken together, contemporary β-lactamases of all Ambler classes can potentially contribute to cefiderocol resistance development and can acquire mutations allowing them to adapt to increasing cefiderocol concentration. At the same time, resistance development caused clinically important cross-resistance, especially against ceftazidime combinations. Summary Despite the reported higher stability of cefiderocol against β-lactamase hydrolysis, we show that the expression of β-lactamases from different Ambler classes significantly contributes to cefiderocol resistance and that these enzymes have the evolutionary potential to evolve towards increasing cefiderocol concentrations.