Anthropic activity in Antarctica has been increasing considerably in recent years, which could have an important impact on the local microbiota affecting multiple features, including the bacterial resistome. As such, our study focused on determining the antibiotic-resistance patterns and antibioticresistance genes of bacteria recovered from freshwater samples collected in areas of Antarctica under different degrees of human influence. Aerobic heterotrophic bacteria were subjected to antibiotic susceptibility testing and pcR. the isolates collected from regions of high human intervention were resistant to several antibiotic groups, and were mainly associated with the presence of genes encoding aminoglycosides-modifying enzymes (AMes) and extended-spectrum β-lactamases (eSBLs). Moreover, these isolates were resistant to synthetic and semi-synthetic drugs, in contrast with those recovered from zones with low human intervention, which resulted highly susceptible to antibiotics. on the other hand, we observed that zone A, under human influence, presented a higher richness and diversity of antibiotic-resistance genes (ARGs) in comparison with zones B and c, which have low human activity. our results suggest that human activity has an impact on the local microbiota, in which strains recovered from zones under anthropic influence were considerably more resistant than those collected from remote regions.

Antibiotic-resistant bacteria of critical importance for global health such as extended-spectrum beta-lactamases-producing (ESBL)-Escherichia coli have been detected in livestock, dogs, and wildlife worldwide. However, the dynamics of ESBL-E. coli between these animals remains poorly understood, particularly in small-scale farms of low and middle-income countries where contact between species can be frequent. We compared the prevalence of fecal carriage of ESBL-E. coli among 332 livestock (207 cows, 15 pigs, 60 horses, 40 sheep, 6 goats, 4 chickens), 82 dogs, and wildlife including 131 European rabbits, 30 rodents, and 12 Andean foxes sharing territory in peri-urban localities of central Chile. The prevalence was lower in livestock (3.0%) and wildlife (0.5%) compared to dogs (24%). Among 47 ESBL-E. coli isolates recovered, CTX-M-group 1 was the main ESBL genotype identified, followed by CTX-M-groups 2, 9, 8, and 25. ERIC-PCR showed no cluster of E. coli clones by either host species nor locality. To our knowledge, this is the first report of ESBL-E. coli among sheep, cattle, dogs, and rodents of Chile, confirming their fecal carriage among domestic and wild animals in small-scale farms. The high prevalence of ESBL-E. coli in dogs encourages further investigation on their role as potential reservoirs of this bacteria in agricultural settings.

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