Long-term trends in ceftolozane-tazobactam susceptibility among gram-negative pathogens in the United States: a nine-year SMART analysis (2016-2024)
Abstract
Objectives: To evaluate trends in the susceptibility of clinical Enterobacterales and Pseudomonas aeruginosa from the USA to ceftolozane/tazobactam.
Methods: The SMART surveillance programme collected 30 658 Enterobacterales and 7454 P. aeruginosa isolates from 37 unique clinical sites in the USA from 2016 to 2024. Nine sites contributed isolates each year. MICs were determined by broth microdilution testing and interpreted using 2025 CLSI breakpoints. Ceftolozane/tazobactam nonsusceptible Enterobacterales were examined for β-lactamase carriage.
Results: Overall, 93.9% and 95.8% of clinical isolates of Enterobacterales and P. aeruginosa were susceptible to ceftolozane/tazobactam, respectively. Considering all participating sites, annual percent susceptible values for ceftolozane/tazobactam against Enterobacterales ranged from 95.3% (2018, n = 3657) to 92.0% (2024, n = 3249) with a statistically significant decreasing trend (P n = 1609) to 91.4% susceptible (2024, n = 1544); P = 0.007]. Including all sites, P. aeruginosa percent susceptible values for ceftolozane/tazobactam remained consistent from 2016 (95.0%) to 2024 (95.0%) [range: 94.5% (2017, n = 991) to 96.9% (2020, n = 817)]. However, considering solely the consistently contributing sites, the rate of ceftolozane/tazobactam susceptibility increased [P = 0.013; range: 91.9% (2017, n = 371) to 96.4% (2024, n = 391)]. The incidence of NDM metallo-β-lactamase and CTX-M ESBLs among ceftolozane/tazobactam nonsusceptible…
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