Nationwide Surveillance on Antimicrobial Resistance Profiles of Enterococcus faecium and Enterococcus faecalis Isolated from Healthy Food Animals in South Korea, 2010 to 2019

Abstract

Intestinal commensal bacteria are considered good indicators for monitoring antimicrobial resistance. We investigated the antimicrobial resistance profiles and resistance trends of Enterococcus faecium and Enterococcus faecalis isolated from food animals in Korea between 2010 and 2019. E. faecium and E. faecalis, isolated from chickens and pigs, respectively, presented a relatively high resistance rate to most of the tested antimicrobials. We observed high ciprofloxacin (67.9%), tetracycline (61.7%), erythromycin (59.5%), and tylosin (53.0%) resistance in E. faecium isolated from chickens. Similarly, more than half of the E. faecalis isolates from pigs and chickens were resistant to erythromycin, tetracycline and tylosin. Notably, we observed ampicillin, daptomycin, tigecycline and linezolid resistance in a relatively small proportion of enterococcal isolates. Additionally, the enterococcal strains exhibited an increasing but fluctuating resistance trend (p < 0.05) to some of the tested antimicrobials including daptomycin and/or linezolid. E. faecalis showed higher Multidrug resistance (MDR) rates than E. faecium in cattle (19.7% vs. 8.6%, respectively) and pigs (63.6% vs. 15.6%, respectively), whereas a comparable MDR rate (≈60.0%) was noted in E. faecium and E. faecalis isolated from chickens. Collectively, the presence of antimicrobial-resistant Enterococcus in food animals poses a potential risk to public health.

Bacterial Antibiotic Resistance: The Most Critical Pathogens

“…E. faecium is considered a MDR bacteria since it is intrinsically resistant to aminoglycoside like tobramycin, kanamycin, gentamicin being capable of producing aminoglycoside-modifying enzymes (AMEs) including aminoglycoside nucleotidyltransferases (ANTs) aminoglycoside acetyltransferases (AACs) and aminoglycoside phosphotransferases (APHs) [109]. Moreover, mutations within the rpsL gene, which encodes the ribosomal protein S12, can result in high level resistance to streptomycin [106,109].…”

“…faecium is considered a MDR bacteria since it is intrinsically resistant to aminoglycoside like tobramycin, kanamycin, gentamicin being capable of producing aminoglycoside-modifying enzymes (AMEs) including aminoglycoside nucleotidyltransferases (ANTs) aminoglycoside acetyltransferases (AACs) and aminoglycoside phosphotransferases (APHs) [109]. Moreover, mutations within the rpsL gene, which encodes the ribosomal protein S12, can result in high level resistance to streptomycin [106,109]. Moreover, high-level fluoroquinolones resistance in E. faecium is most frequently linked with point mutations in gyrA and parC genes that encode subunits A of DNA gyrase and topoisomerase IV or with efflux transporter NorA that pump out these drugs [106].…”

Prevalence and Characteristics of Phenicol-Oxazolidinone Resistance Genes in Enterococcus Faecalis and Enterococcus Faecium Isolated from Food-Producing Animals and Meat in Korea

“…The functionally active Tn554 can be excised from their host DNA and generate circular forms that precede the integration of the transposon into a target sequence [ 23 , 24 ]. A similar genetic arrangement of optrA and Tn554 was identified in enterococci and staphylococci [ 13 , 16 ], suggesting that optrA can be mediated for transfer between different bacterial genus and species. The optrA gene was flanked by transposon or insertion sequences, indicating that a mobile genetic element mediates the horizontal transfer of optrA between bacteria of different genera, which should be given more attention to avoid disseminating the oxazolidinone resistance gene in the environment.…”

“…Knowledge of the distribution of antimicrobial-resistant strains in the food chain and food animals is important in determining the potential risk to human health [ 13 ]. Here, we investigated the prevalence and genetic characterization of phenicol-oxazolidinone resistance genes to understand better the phenicol-oxazolidinone resistance profiles of enterococci isolates obtained from food animals, animal carcass, and meat in Korea.…”

“…The poxtA gene was located on plasmids in two enterococci strains. The poxtA gene is often surrounded by bacteria insertion sequences on the plasmid in staphylococci or enterococci strains [ 13 , 16 ]. Our data showed that all poxtA found on plasmids were flanked by IS1216E, similar to the previous studies [ 9 , 16 , 25 ].…”