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 β-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 β-lactam-NS. Multidrug resistance (MDR) was defined as NS to ≥1 drug in ≥3 drug classes, and extensively drug-resistant (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 β-lactams. C–T was active against 13/16 COL-NS isolates.