Abstract
In extreme environments, such as the Arctic region, the anthropogenic influence is low and the presence of antimicrobial-resistant bacteria is unexpected. In this study, we screened wild reindeer (Rangifer tarandus platyrhynchus) from the Svalbard High Arctic Archipelago for antimicrobial-resistant Escherichia coli and performed in-depth strain characterisation. Using selective culturing of faecal samples from 55 animals, resistant E. coli were isolated and subjected to minimum inhibitory concentration (MIC) determination, conjugation experiments and whole-genome sequencing. Twelve animals carried antimicrobial-resistant E. coli. Genomic analysis showed IncF plasmids as vectors both for resistance and virulence genes in most strains. Plasmid-associated genes encoding resistance to ampicillin, sulfonamides, streptomycin and trimethoprim were found in addition to virulence genes typical for colicin V (ColV)-producing plasmids. Comparison with previously reported IncF ColV plasmids from human and animal hosts showed high genetic similarity. The plasmids were detected in E. coli sequence types (STs) previously described as hosts for such plasmids, such as ST58, ST88 and ST131. Antimicrobial-resistant E. coli were detected from Svalbard reindeer. Our findings show that successful hybrid antimicrobial resistance-ColV plasmids and their host strains are widely distributed also occurring in extreme environmental niches such as arctic ecosystems. Possible introduction routes of resistant bacterial strains and plasmids into Svalbard ecosystems may be through migrating birds, marine fish or mammals, arctic fox (Vulpes lagopus) or via human anthropogenic activities such as tourism.
Highlights
Recent studies have shown that antimicrobial-resistant bacteria can disseminate and persist in complete absence of selection pressure from antimicrobial agents, as exemplified by the expansion of third-generation cephalosporin resistance among Escherichia coli in Nordic broiler production where use of antimicrobials is almost absent [1,2,3]
Genes responsible for antimicrobial resistance were the same as those commonly occurring in isolates from humans and animals, such as the blaTEM-1 gene encoding ampicillin resistance, sul1 and sul2 mediating resistance to sulfonamides, tetA and tetB encoding tetracycline resistance, strA–strB and aadA encoding streptomycin resistance, and the integron-associated gene cassettes drfA1 and dfrA5 encoding resistance to trimethoprim
We demonstrated that wild reindeer in a remote high arctic ecosystem harboured antimicrobial-resistant E. coli
Summary
Recent studies have shown that antimicrobial-resistant bacteria can disseminate and persist in complete absence of selection pressure from antimicrobial agents, as exemplified by the expansion of third-generation cephalosporin resistance among Escherichia coli in Nordic broiler production where use of antimicrobials is almost absent [1,2,3]. A recent study found genes encoding antimicrobial resistance from soil samples taken at the Svalbard High Arctic Archipelago [10]. Svalbard, which is Norwegian territory, is an archipelago located between the Norwegian mainland and the North Pole. These islands consist of large areas with untouched nature, arctic climate and very low human population density, restricted to a few smaller villages. The aim of this study was to investigate whether Svalbard reindeer in a remote ‘antibiotic free’ arctic environment can be carriers of antimicrobial-resistant E. coli. We performed in-depth sequencebased bacterial characterisation, with special focus on plasmid content, to evaluate possible source and routes of introduction for antimicrobial-resistant bacteria to these environments
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