Antimicrobial activity of ceftolozane/tazobactam tested against contemporary (2015-2017) Pseudomonas aeruginosa isolates from a global surveillance programme

Objectives: Ceftolozane/tazobactam (C-T) is an antimicrobial combination of an antipseudomonal cephalosporin and a beta-lactamase inhibitor. C-T has been approved in >60 countries for complicated urinary tract infections, acute pyelonephritis, complicated intra-abdominal infections in combination with metronidazole, and was recently approved for hospital-acquired bacterial pneumonia. In this study, data for Pseudomonas aeruginosa isolates consecutively collected from various infection types in hospitalised patients from 2015 to 2017 were analysed. Methods: A total of 6836 P. aeruginosa isolates were collected from 104 hospitals in four continents and were tested for susceptibility to C-T by CLSI broth microdilution methodology at JMI Laboratories using CLSI (2018) breakpoints. Other agents tested included amikacin, ceftazidime (CAZ), colistin (COL), levofloxacin (LVX), meropenem (MEM) and piperacillin/tazobactam (TZP). Resistance phenotypes analysed included CAZ-non-susceptible (CAZ-NS), COL-NS, MEM-NS, LVX-NS, TZP-NS and p-lactam-NS. Multidrug resistance (MDR) was defined as NS to >1 drug in >3 drug classes, and extensively drugresistant (XDR) was defined as NS to >= 1 agent in all but 2 or fewer antimicrobial classes. Results: The most common infection from which P. aeruginosa was isolated was pneumonia (51.6%), followed by skin and skin-structure infection (22.2%) and bloodstream infection (15.3%). Percentage susceptibility to C-T varied by region: 98.2% in North America; 94.8% in Asia-Pacific; 90.8% in Latin America; and 89.1% in Europe. Conclusion: C-T had potent activity against P. aeruginosa isolated from patients in hospitals in four continents. C-T was more active than all comparators, except COL, and maintained activity against MDR and XDR isolates and isolates NS to all four tested beta-lactams. C-T was active against 13/16 COL-NS isolates. (C) 2019 International Society for Antimicrobial Chemotherapy. Published by Elsevier Ltd.