Comparative In Vitro Activity of Ceftolozane/Tazobactam against Clinical Isolates of and from Five Latin American Countries.

Background: Ceftolozane/tazobactam (C/T) is a combination of an antipseudomonal oxyiminoaminothiazolyl cephalosporin with potent in vitro activity against and tazobactam, a known β-lactamase inhibitor. The aim of this study was to evaluate the activity of C/T against clinical isolates of and collected from five Latin American countries between 2016 and 2017, before its clinical use in Latin America, and to compare it with the activity of other available broad-spectrum antimicrobial agents.

Methods: a total of 2760 clinical isolates (508 and 2252 ) were consecutively collected from 20 hospitals and susceptibility to C/T and comparator agents was tested and interpreted following the current guidelines.

Results: according to the CLSI breakpoints, 68.1% (346/508) of and 83.9% (1889/2252) of isolates were susceptible to C/T. Overall, C/T demonstrated higher in vitro activity than currently available cephalosporins, piperacillin/tazobactam and carbapenems when tested against , and its performance in vitro was comparable to fosfomycin. When tested against , it showed higher activity than cephalosporins and piperacillin/tazobactam, and similar activity to ertapenem.

Conclusions: these results show that C/T is an active β-lactam agent against clinical isolates of and .