<i>In Vitro</i> Activity of Cefiderocol, a Siderophore Cephalosporin, against Multidrug-Resistant Gram-Negative Bacteria

Abstract

Cefiderocol is a parenteral siderophore cephalosporin with a catechol-containing 3' substituent. We evaluated its MICs against Gram-negative bacteria, using iron-depleted Mueller-Hinton broth. The panel comprised 305 isolates of <i>Enterobacterales</i>, 111 of <i>Pseudomonas aeruginosa</i>, and 99 of <i>Acinetobacter baumannii</i>, all selected for carbapenem resistance and multidrug resistance to other agents. At 2 and 4 μg/ml, cefiderocol inhibited 78.7 and 92.1%, respectively, of all <i>Enterobacterales</i> isolates tested, with rates of 80 to 100% for isolates with all modes of carbapenem resistance except NDM enzymes (41.0% inhibited at 2 μg/ml and 72.1% at 4 μg/ml) or combinations of extended-spectrum β-lactamase (ESBL) and porin loss (61.5% inhibited at 2 μg/ml and 88.5% at 4 μg/ml). Cefiderocol also inhibited 81.1 and 86.5% of all <i>P. aeruginosa</i> isolates at 2 and 4 μg/ml, respectively, with rates of 80 to 100% for isolates with VIM, IMP, GES, or VEB β-lactamases and slightly lower rates for those with NDM (45.5% at 2 μg/ml and 72.7% at 4 μg/ml) and PER (66.7% at 2 μg/ml and 73.3% at 4 μg/ml) enzymes; 63.3% of <i>P. aeruginosa</i> isolates were inhibited at the FDA's 1-μg/ml breakpoint. Lastly, cefiderocol at 2 and 4 μg/ml inhibited 80.8 and 88.9% of the <i>A. baumannii</i> isolates, respectively, with rates of >85% for isolates with OXA-51-like, -23, -24, or -58 enzymes and 50% at 2 μg/ml and 80% at 4 μg/ml for those with NDM carbapenemases. Dipicolinic acid and avibactam weakly potentiated cefiderocol against <i>Enterobacterales</i> isolates with metallo-β-lactamases (MBLs) and serine carbapenemase, respectively, indicating incomplete β-lactamase stability.