Multicenter Evaluation of Ceftazidime-Avibactam and Ceftolozane-Tazobactam Inhibitory Activity against Meropenem-Nonsusceptible Pseudomonas aeruginosa from Blood, Respiratory Tract, and Wounds

Abstract

The recent escalation of occurrences of carbapenem-resistant <i>Pseudomonas aeruginosa</i> has been recognized globally and threatens to erode the widespread clinical utility of the carbapenem class of compounds for this prevalent health care-associated pathogen. Here, we compared the <i>in vitro</i> inhibitory activity of ceftazidime-avibactam and ceftolozane-tazobactam against 290 meropenem-nonsusceptible <i>Pseudomonas aeruginosa</i> nonduplicate clinical isolates from 34 U.S. hospitals using reference broth microdilution methods. Ceftazidime-avibactam and ceftolozane-tazobactam were active, with ceftolozane-tazobactam having significantly higher inhibitory activity than ceftazidime-avibactam. The heightened inhibitory activity of ceftolozane-tazobactam was sustained when the site of origin (respiratory, blood, or wound) and nonsusceptibility to other β-lactam antimicrobials was considered. An extensive genotypic search for enzymatically driven β-lactam resistance mechanisms revealed the exclusive presence of the VIM metallo-β-lactamase among only 4% of the subset of isolates nonsusceptible to ceftazidime-avibactam, ceftolozane-tazobactam, or both. These findings suggest an important role for both ceftazidime-avibactam and ceftolozane-tazobactam against carbapenem-nonsusceptible <i>Pseudomonas aeruginosa</i> Further <i>in vitro</i> and <i>in vivo</i> studies are needed to better define the clinical utility of these novel therapies against the increasingly prevalent threat of multidrug-resistant <i>Pseudomonas aeruginosa</i>.