Jan, Hao-EnHao-EnJanWang, Jiun-LingJiun-LingWangLee, Nan-YaoNan-YaoLeeHsueh, Shun-ChungShun-ChungHsuehYU-TSUNG HUANGKo, Wen-ChienWen-ChienKoPO-REN HSUEH2026-04-212026-04-212026-0109248579https://scholars.lib.ntu.edu.tw/handle/123456789/737403Objective The aim of this study is to investigate the trends in ceftazidime-avibactam (CZA) resistance among clinical isolates of Citrobacter freundii, Morganella morganii, Providencia spp., and Serratia marcescens globally using the database from Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2016–2023. Methods A total of 18,908 isolates (4,231 C. freundii , 4658 M. morganii , 3,570 Providencia spp ., and 6449 S. marcescens ) from five continents were analysed. Antimicrobial susceptibility testing of these isolates was conducted using the broth microdilution method. Results The CZA resistance rate was the highest in Providencia spp. (8.8%), followed by C. freundii (3.4%), S. marcescens (1.5%), and M. morganii (0.6%). An increasing resistance trend was noted in C. freundii (R² = 0.817) and S. marcescens (R² = 0.995) during the study period. The resistance rate in Providencia spp. peaked in 2020–2021 (R² = 0.610), while that in M. morganii remained sporadically low. Regionally, the biannual resistant rate of C. freundii rose from 6.7% to 13.0% in Asia, 0% to 7.8% in Latin America, and 0% to 7.0% in East Asia (2016–2017 vs . 2022–2023). Furthermore, among carbapenem-resistant isolates, CZA resistance was noted in 91.1% of Providencia spp., 78.8% of C. freundii , 34.9% of S. marcescens , and 60% of M. morganii. The predominant carbapenemase gene was bla NDM in Providencia spp. (82.6%), M. morganii (69.2%), and C. freundii (42.0%), and bla KPC in S. marcescens (45.3%) among carbapenemase-producing isolates. Conclusions CZA resistance is emerging across diverse Enterobacterales species, and exhibits geographic and temporal variability, and warrants continued global surveillance.enfalseAntimicrobial Testing Leadership and Surveillance programmeCarbapenemase genesCeftazidime-avibactam resistanceCitrobacter freundiiMorganella morganiiProvidencia spp.Serratia marcescensjournal article10.1016/j.ijantimicag.2025.107669412604022-s2.0-105023994709