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 <i>Enterococcus faecium</i> and <i>Enterococcus faecalis</i> isolated from food animals in Korea between 2010 and 2019. <i>E. faecium</i> and <i>E. faecalis,</i> 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 <i>E. faecium</i> isolated from chickens. Similarly, more than half of the <i>E. faecalis</i> 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 (<i>p</i> < 0.05) to some of the tested antimicrobials including daptomycin and/or linezolid. <i>E. faecalis</i> showed higher Multidrug resistance (MDR) rates than <i>E. faecium</i> 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 <i>E. faecium</i> and <i>E. faecalis</i> isolated from chickens. Collectively, the presence of antimicrobial-resistant <i>Enterococcus</i> in food animals poses a potential risk to public health.