Emerging co-occurrence of mcr-10 and broad-spectrum β-lactamase genes in Enterobacterales from surface waters in Brazil.

Aquatic ecosystems play a key role in the spread of antimicrobial resistance genes (ARGs), especially mcr-type and β-lactamase genes. The occurrence of β-lactamases and the mcr-10 genes has emerged among Enterobacterales species across the world; however, this phenomenon had never been reported in Brazil until now. We performed a surveillance study focusing on the spread of the mcr-type genes in WHO critical bacterial priority pathogens isolated from aquatic ecosystems. For this, 132 surface water samples from rivers and streams were collected between 2021 and 2023 and studied, and 492 bacterial strains were obtained. Accordingly, 14 strains (11 Escherichia coli and three Klebsiella pneumoniae species complex) resistant to third-generation cephalosporins or carbapenems were identified as harboring the mcr-10 gene. These strains belonged to international, unusual, and novel clones. In addition, several ARGs were detected, spotlighting ESBL- and carbapenemase-encoding genes, which confer resistance to clinically important antimicrobials. Most virulence genes and plasmid replicons were found, and two novel multireplicon plasmids were identified in a Klebsiella quasipneumoniae strain. These findings highlight the first report of the mcr-10 gene in Brazil and the early dissemination throughout the environmental sector. Therefore, the identification of Enterobacterales strains co-producing mcr-10 and broad-spectrum-β-lactamase genes draws attention to a new trend in antimicrobial resistance mediated by critical pathogens in the environment.