Ceftazidime-avibactam resistance among clinical isolates of Citrobacter freundii, Morganella morganii, Providencia spp. and Serratia marcescens across five continents: Data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2016-2023.

OBJECTIVE

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 blaNDM in Providencia spp. (82.6%), M. morganii (69.2%), and C. freundii (42.0%), and blaKPC 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.