ABSTRACT
Abstract Introduction The incidence of antimicrobial resistance is increasing in many parts of the world. The focus of this report is to examine changes in antimicrobial resistance epidemiology among clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected in six Latin American countries as part of the Antimicrobial Testing Leadership and Surveillance (ATLAS) program from 2015 to 2020, with a focus on the in vitro activity of ceftazidime-avibactam against Multidrug-Resistant (MDR) isolates. Methods Non-duplicate, clinical isolates of Enterobacterales (n= 15,215) and P. aeruginosa (n= 4,614) collected by 40 laboratories in Argentina, Brazil, Chile, Colombia, Mexico, and Venezuela, from 2015 to 2020, underwent centralized Clinical Lab Standards Institute (CLSI) broth microdilution susceptibility testing. Minimum Inhibitory Concentration (MIC) values were interpreted using 2022 CLSI breakpoints. An MDR phenotype was defined by resistance to ≥ 3 of seven sentinel agents. Results In total, 23.3% of Enterobacterales and 25.1% of P. aeruginosa isolates were MDR. Annual percent MDR values for Enterobacterales were stable from 2015 to 2018 (21.3% to 23.7% year) but markedly increased in 2019 (31.5%) and 2020 (32.4%). Annual percent MDR values for P. aeruginosa were stable from 2015 to 2020 (23.0% to 27.6% year). Isolates were divided into two 3-year time-periods, 2015‒2017 and 2018‒2020, for additional analyses. For Enterobacterales, 99.3% of all isolates and 97.1% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 97.2% and 89.3% of isolates, respectively, from 2018‒2020. For P. aeruginosa, 86.6% of all isolates and 53.9% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 85.3% and 45.3% of isolates, respectively, from 2018‒2020. Among individual countries, Enterobacterales and P. aeruginosa collected in Venezuela showed the greatest reductions in ceftazidime-avibactam susceptibility over time. Conclusion MDR Enterobacterales increased in Latin America from 22% in 2015 to 32% in 2020 while MDR P. aeruginosa remained constant at 25%. Ceftazidime-avibactam remains highly active against all clinical isolates of both Enterobacterales (97.2% susceptible, 2018‒2020) and P. aeruginosa (85.3%), and inhibited more MDR isolates (Enterobacterales, 89.3% susceptible, 2018‒2020; P. aeruginosa, 45.3%) than carbapenems, fluoroquinolones, and aminoglycosides.