Comparison of ceftazidime-avibactam and ceftolozane-tazobactam in vitro activities when tested against gram-negative bacteria isolated from patients hospitalized with pneumonia in United States medical centers (2017–2018)

Abstract

Clinical isolates were consecutively collected from 70 United States medical centers in 2017–2018 and susceptibility tested by reference broth microdilution methods at a central laboratory. The most active agents against Enterobacterales (n = 3269) were ceftazidime-avibactam (99.9% susceptible), amikacin (98.7% susceptible), meropenem (97.4% susceptible), and tigecycline (94.6% susceptible), but only ceftazidime-avibactam and tigecycline retained good activity (≥90% susceptible) against carbapenem-resistant Enterobacterales (97.5% and 92.4% susceptible, respectively). The most active agents against multidrug-resistant (MDR) Enterobacterales were ceftazidime-avibactam (99.2% susceptible) and amikacin (90.9% susceptible), whereas ceftolozane-tazobactam and meropenem were active against only 53.8% and 78.1% of these organisms, respectively. Among ESBL-producing Enterobacterales (excluding carbapenemase-producing), susceptibility rates for ceftazidime-avibactam, ceftolozane-tazobactam, and meropenem were 100.0%, 84.1%, and 98.9%, respectively. Ceftazidime-avibactam and ceftolozane-tazobactam were very active against P. aeruginosa (n = 2215) and exhibited similar susceptibility rates (96.0% and 95.9% susceptible, respectively), including against meropenem-nonsusceptible (87.2% and 87.3% susceptible, respectively) and MDR (83.5% and 83.7% susceptible, respectively) isolates.