Antimicrobial resistance occurrence in the South American Sea Lion (Otaria flavescens) from Patagonia, Argentina, from a One Health perspective

Under the "One Health" concept, this paper aims to explore the occurrence of antimicrobial resistance in Enterobacterales (i.e., Escherichia coli and Salmonella enterica) among the South American Sea Lions on Argentina's northern Patagonian coast. From 177 fecal samples collected, conventional protocols were used to isolate E. coli and S. enterica. Antimicrobials classified as critically important by the WHO were evaluated by disk diffusion and agar spot (colistin) methods. Molecular tools were used to detect mcr genes as needed. A total of 176 antimicrobial-susceptible E. coli strains and 14 S. enterica strains were recovered. Twelve E. coli strains were colistin resistant (agar spot positive) but PCR negative for the mcr-1 to mcr-5 genes. Whole-genome sequencing revealed a chromosomal mutation, coding for Val161Gly change in PmrB protein, as the colistin resistance mechanism in one of these isolates. This study provides knowledge on AMR surveillance in wildlife associated with the marine environment in South America.