Antimicrobial activity of ceftolozane–tazobactam tested against gram-negative contemporary (2015–2017) isolates from hospitalized patients with pneumonia in US medical centers

Abstract

Pseudomonas aeruginosa (n = 1531) and Enterobacteriaceae (n = 2373) clinical isolates from hospitalized patients with pneumonia were collected from 31 US medical centers during 2015–2017. Isolates were susceptibility tested against ceftolozane–tazobactam and comparators by broth microdilution. Results from intensive care unit (ICU) patients and patients with ventilator-associated bacterial pneumonia (VABP) were analyzed separately. Ceftolozane–tazobactam was very active against P. aeruginosa (MIC50/90, 0.5/2 mg/L; 97.5% susceptible), including multidrug-resistant (87.9% susceptible) and extensively drug-resistant (82.9% susceptible). Ceftolozane–tazobactam inhibited 90.3% of Enterobacteriaceae isolates (MIC50/90, 0.25/2 mg/L), including non–carbapenem-resistant Enterobacteriaceae isolates with an extended-spectrum β-lactamase phenotype (85.7% susceptible). Ceftolozane–tazobactam activity was stable against P. aeruginosa regardless of the US census division or ICU and VABP subsets (>90%); small differences were noted among Enterobacteriaceae isolates from the Middle Atlantic (range 78.3–88.9%) and West South Central (range 86.4–89.2%) divisions. These in vitro results indicate that ceftolozane–tazobactam may represent a valuable option for hospital-acquired bacterial pneumonia and VABP caused by Enterobacteriaceae and P. aeruginosa in the United States.