Abstract
The aim of this work was to detect Escherichia coli isolates displaying resistance to oxyimino-cephalosporins, quinolones, and colistin in feces from livestock in Uruguay. During 2016–2019, fecal samples from 132 broiler and layer chicken flocks, 100 calves, and 50 pigs, were studied in Uruguay. Samples were cultured on MacConkey Agar plates supplemented with ciprofloxacin, ceftriaxone, or colistin. E. coli isolates were identified by mass spectrometry and antibiotic susceptibility testing was performed by disk diffusion agar method and colistin agar test. Antibiotic resistance genes were detected by polymerase chain reaction and sequencing. The most frequently detected resistance gene was qnrB19, recovered from 87 animals. Regarding plasmid-mediated quinolone resistance genes, qnrS1 was the second in prevalence (23 animals) followed by qnrE1, found in 6 chickens and two calves. Regarding resistance to oxyimino-cephalosporins, 8 different β-lactamase genes were detected: blaCTX−M−8 and blaCMY−2 were found in 23 and 19 animals, respectively; next, blaCTX−M−2 and blaSHV−12 in 7 animals each, followed by blaCTX−M−14 in 5, blaCTX−M−15 and blaSHV2a in 2, and blaCTX−M−55 in a single animal. Finally, the mcr-1 gene was detected only in 8 pigs from a single farm, and in a chicken. Isolates carrying blaCMY−2 and blaSHV−12 were also found in these animals, including two isolates featuring the blaCMY−2/mcr-1 genotype. To the best of our knowledge, this is the first work in which the search for transferable resistance to highest priority critically important antibiotics for human health is carried out in chickens and pigs chains of production animals in Uruguay.
Highlights
The interaction between humans and animals is quite diverse and may lead to cases of zoonosis and/or anthropozoonosis (1)
In the present work we selected 73 E. coli isolates obtained from 100 calves, 141 isolates obtained from 132 chickens, and 99 isolates obtained from 50 pigs, yielding genotype/studied animal ratios of 0.73 (73/100), 1.08 (140/132), and 1.77 (99/50) for calves, poultry, and swine, respectively
30% of the E. coli resistant genotypes recovered from calves were linked to transferable resistance genes (22/73); in poultry, and swine, the frequency of isolates harboring transferable resistance genes was 55% (78/140) and 76% (75/99), respectively (Table 1)
Summary
The interaction between humans and animals is quite diverse and may lead to cases of zoonosis and/or anthropozoonosis (1). Over the past decades the aforementioned interaction has constantly increased worldwide partly due to animal husbandry practices, the growth of the companion animal market, climate change, and ecosystem disruption In this context, bacterial transmission may occur through food products (e.g., meat or eggs) or through direct contact, in particular in farmers, veterinarians, or abattoir workers (2). Anthropogenic changes to the ecosystem increase the number of shared habitats between humans and animals, exposing both to new pathogens In this regard, several authors have described the occurrence in humans and several animal species of the pandemic strain, Escherichia coli 025:H4 ST131, carrying the extended-spectrum beta-lactamase CTX-M-15. This particular event indicates an interspecies transmission from humans to pets and livestock and has been described across Europe (5)
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