| Summary: | The increasing prevalence of multi-drug resistant (MDR) <i>Escherichia coli</i> in distinct ecological niches, comprising water sources and food-producing animals, such as fish species, has been widely reported. In the present study, quinolone-resistant <i>E. coli</i> isolates from <i>Arapirama gigas</i>, a major fish species in the Brazilian Amazon rivers and fish farms, were characterized regarding their antimicrobial susceptibility, virulence, and genetic diversity. A total of forty (40) specimens of <i>A. gigas</i>, including 20 farmed and 20 wild fish, were included. Thirty-four quinolone-resistant <i>E. coli</i> isolates were phenotypically tested by broth microdilution, while resistance and virulence genes were detected by PCR. Molecular epidemiology and genetic relatedness were analyzed by MLST and PFGE typing. The majority of isolates were classified as MDR and detected harboring <i>bla</i><sub>CTX-M</sub>, <i>qnrA</i> and <i>qnrB</i> genes. Enterotoxigenic <i>E. coli</i> pathotype (ETEC) isolates were presented in low prevalence among farmed animals. MLST and PFGE genotyping revealed a wide genetic background, including the detection of internationally spread clones. The obtained data point out <i>A. gigas</i> as a reservoir in Brazilian Amazon aquatic ecosystems and warns of the interference of AMR strains in wildlife and environmental matrices.
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