LAUSR

OBJECTIVES To evaluate the in vitro activity of ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, imipenem-relebactam, and comparator agents against contemporary Pseudomonas aeruginosa isolates from United States (US) hospitals. METHODS 3,184 isolates were consecutively collected from 71 US medical centers in 2020-2021 and susceptibility tested by reference broth microdilution. Clinical Laboratory Standard Institute (CLSI) breakpoints were applied. RESULTS Ceftazidime-avibactam (97.0% susceptible [S]), ceftolozane-tazobactam (98.0%S), imipenem-relebactam (97.3%S), and tobramycin (96.4%S) were the most active agents against the aggregate P. aeruginosa isolate collection and retained good activity against piperacillin-tazobactam-nonsusceptible, meropenem-nonsusceptible, and multidrug-resistant (MDR) isolates. All other antimicrobials tested showed limited activity against piperacillin-tazobactam-nonsusceptible, meropenem-nonsusceptible, and MDR isolates. The most common infection types were pneumonia (45.9%), skin and skin structure infection (19.0%), urinary tract infection (17.0%), and bloodstream infection (11.7%); ceftazidime-avibactam, ceftolozane-tazobactam, and imipenem-relebactam showed consistent activity against isolates from these infection types. Susceptibility to piperacillin-tazobactam and meropenem were lower among isolates from pneumonia compared to other infection types. CONCLUSIONS Ceftazidime-avibactam, ceftolozane-tazobactam, and imipenem-relebactam were highly active and exhibited similar coverage against a large contemporary collection of P. aeruginosa isolates from US hospitals. Cross-resistance among the newer BL/BLIs varied markedly; ≥72.1% of isolates resistant to one of the three newer BL/BLI approved for P. aeruginosa treatment remained susceptible to at least one of the other two, indicating that all 3 should be tested in the clinical laboratory. These 3 BL/BLI agents represent valuable therapeutic options for P. aeruginosa infection treatment.