Does Shiga Toxin-Producing Escherichia coli and Listeria monocytogenes Contribute Significantly to the Burden of Antimicrobial Resistance in Uruguay?

Shiga toxin-producing (STEC) and are worldwide recognized zoonotic pathogens. Recent reports have emerged about the circulation of antimicrobial-resistant STEC and isolates. To assess the frequency of antimicrobial resistance and related genes in these pathogens, we studied 45 STEC and 50 isolates locally recovered from different sources. Antimicrobial susceptibility testing was performed by disk-diffusion method, and the genomic sequences of three selected STEC and from all 50 isolates were analyzed for antibiotic resistance genes. Four STEC and three isolates were phenotypically resistant to at least one of the antibiotics tested. Resistance genes (3″)-Ib, (3')-Ia, (6)-Id, , 2, (A), and A) were found in a human STEC ampicillin-resistant isolate. All isolates harbored f L, , and . Overall resistance in and STEC was low or middle. However, the high load of resistance genes found, even in susceptible isolates, suggests that these pathogens could contribute to the burden of antimicrobial resistance.