Epidemiology of colistin resistance mediated by mcr-1 in carbapenemase-producing Enterobacterales in Ecuador in three periods from 2016 to 2022.

Carbapenemase-producing Enterobacterales (CPE) have increased in the last decade. In low-income countries, colistin is considered a last resort antimicrobial to treat CPE infections, whose most worrisome mechanism of resistance is MCR-1 production. This study aims to understand the epidemiology of colistin resistance in CPE in the region, through the surveillance of the mcr-1 gene in CPE isolates in Ecuador. A total of 361 CPE isolates were collected across three periods, from 2016 to 2022. Colistin resistance was assessed using the broth microdilution method and the most frequent carbapenemase-encoding genes and the mcr-1 gene were studied. Colistin resistance rate increased from 3.76% to 23.74% during the study period. The mcr-1 gene was not identified in any of the isolates studied and Klebsiella pneumoniaeblaKPC was the most prevalent microorganism (n=322; 89.20%). In conclusion, colistin resistance increased in CPE in Ecuador and was not mediated by the mcr-1 gene. Our results highlight the need to closely monitor national politics on antimicrobial resistance under the One Health Approach.