Abstract
Extended-spectrum β-lactam antimicrobials have been broadly used in food animals and humans to control infectious diseases. However, the emergence and rapid spread of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae, mainly Escherichia coli, have seriously threatened global health in recent decades. In this study, we determined the prevalence, antimicrobial susceptibility, and genetic properties of ESBL-producing E. coli (ESBL-EC) strains isolated from food animals in South Korea. A total of 150 fecal samples from healthy chickens (n = 34), pigs (n = 59), and cattle (n = 57) were screened from January to July 2018. Among these, 77 non-duplicate cefotaxime-resistant ESBL-EC strains were isolated from 32 chicken, 41 pig, and 4 cattle samples, with the corresponding occurrence rates of 94.1, 69.5, and 7.0%, respectively. All the isolates showed multidrug resistance (MDR) and produced at least one type of β-lactamase, including CTX-M (98.7%) and TEM (40.3%). CTX-M-14 (53.1%), CTX-M-55 (53.7%), and CTX-M-65 (50.0%) were the predominant genotypes in the chicken, pig, and cattle samples, respectively. Multilocus sequence typing revealed 46 different sequence types (STs), including the human-associated extraintestinal pathogenic E. coli ST131 (n = 2), ST10 (n = 5), ST38 (n = 1), ST410 (n = 4), ST354 (n = 2), ST58 (n = 3), ST117 (n = 1), and ST457 (n = 1). To the best of our knowledge, this is the first report of pandemic E. coli ST131 in non-human isolates in South Korea. Our results demonstrate the high prevalence and diversity of MDR-ESBL-EC in food animals and highlight them as potential pathogenic ESBL-EC reservoirs that may pose a high risk to human health.
Highlights
Extended-spectrum β-lactam antimicrobials have been widely used to treat bacterial infections both in humans and animals
To investigate the prevalence of ESBL-producing E. coli (ESBL-EC) strains in food animals, we cultured a total of 150 fecal samples from 34 chickens, 59 pigs, and 57 cattle on MacConkey agar plates containing cefotaxime (2 μg/mL) and purified single colonies on CHROMagar ESBL plates
77 nonduplicate cefotaxime-resistant E. coli strains were isolated from 32 chickens (94.1%), 41 pigs (69.5%), and 4 cattle (7.0%)
Summary
Extended-spectrum β-lactam antimicrobials have been widely used to treat bacterial infections both in humans and animals. Multidrug-resistant (MDR) ESBL-EC pathogens, which pose a serious threat to human health due to the limited treatment options, extensively disseminate among food animals (Ho et al, 2011; Vitas et al, 2018), which are considered to be the primary reservoirs of antimicrobial-resistant enteric bacteria, the routes of transmission to humans are unclear. Such bacteria can presumably pass through the food chain or via close contact and can colonize the intestines of humans (Carattoli, 2008). Previous studies conducted in South Korea have mainly focused on the prevalence and characteristics of ESBL genes of E. coli isolates from food animals (Tamang et al, 2013b; Shin et al, 2017), but their relatedness to human-associated clonal lineages has rarely been investigated
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