Cefdinir binding to a class A β-lactamase revealed by serial cryo-crystallography

One of the most common resistance mechanisms against antibiotics employed by Gram-negative bacteria involves the production of β-lactamases, resulting in rapid hydrolysis of the antibiotic. Extensive use of the early-generation cephalosporins led to the rise of extended-spectrum β-lactamases such as CTX-Ms. Cefdinir is an extended-spectrum third-generation cephalosporin administered since the late 1990s; despite this, there is no reported 3D structure of the antibiotic bound to any β-lactamase or penicillin-binding protein in the PDB. Here, we report the X-ray crystallographic structure of cefdinir-bound CTX-M-14 E166A mutant obtained via serial cryo-crystallography.