Detection of the Phenicol–Oxazolidinone Resistance Gene <i>poxtA</i> in <i>Enterococcus faecium</i> and <i>Enterococcus faecalis</i> from Food-Producing Animals during 2008–2018 in Korea

• Main Authors: Seok-Hyeon Na, Dong-Chan Moon, Mi-Hyun Kim, Hee-Young Kang, Su-Jeong Kim, Ji-Hyun Choi, Abraham-Fikru Mechesso, Soon-Seek Yoon, Suk-Kyung Lim
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Microorganisms
• Subjects: clonal complex 17; <i>Enterococcus</i>; linezolid resistance; <i>poxtA</i>
• Online Access: https://www.mdpi.com/2076-2607/8/11/1839

We aimed to investigate the presence of the phenicol–oxazolidinone resistance gene <i>poxtA</i> in linezolid-resistant enterococci from food-producing animals and analyze its molecular characteristics. We collected 3941 <i>Enterococcus faecium</i> and 5088 <i>E. faecalis</i> isolates from all provinces of South Korea from 2008 to 2018. We found linezolid resistance in 0.79% (94/3941) of <i>E. faecium</i> and 1.22% (62/5088) of <i>E. faecalis</i> isolates. Overall, 23.1% (36/156) of the linezolid-resistant isolates had the <i>poxtA</i> gene, including 31 <i>E. faecium</i> and five <i>E. faecalis</i> isolates. The <i>poxtA</i>-positive enterococci were mainly isolated from chicken (86.1%; 26/36). Fifteen <i>poxtA</i>-harboring isolates co-carried another linezolid-resistance gene, <i>optrA</i>. Eight <i>E. faecium</i> isolates had an N130K mutation in the ribosomal protein L4, while no mutations were observed in <i>E. faecalis</i> isolates. The <i>poxtA</i> gene was transferred into 10 enterococci by conjugation. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) analysis indicated that <i>poxtA</i>-carrying isolates were heterogeneous. Three <i>E. faecium</i> isolates belonged to CC17 (ST32, ST121, and ST491). To our knowledge, this is the first report on the <i>poxtA</i> gene in Korea. Prudent use of antimicrobials and active surveillance on antimicrobial resistance are urgently needed to reduce the risk of dissemination of the linezolid-resistant isolates in humans and animals.