Resistance Profiling and Molecular Characterization of Extended-Spectrum/Plasmid-Mediated AmpC β-Lactamase-Producing <i>Escherichia coli</i> Isolated from Healthy Broiler Chickens in South Korea

• Main Authors: Hyun-Ju Song, Dong Chan Moon, Abraham Fikru Mechesso, Hee Young Kang, Mi Hyun Kim, Ji-Hyun Choi, Su-Jeong Kim, Soon-Seek Yoon, Suk-Kyung Lim
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Microorganisms
• Subjects: broiler; β-lactamase; <i>bla</i> _CTX-M; <i>bla</i> _CMY-2; <i>E. coli</i>; <i>mcr-1</i>
• Online Access: https://www.mdpi.com/2076-2607/8/9/1434

We aimed to identify and characterize extended-spectrum β-lactamase (ESBL)-and/or plasmid-mediated AmpC β-lactamase (pAmpC)-producing <i>Escherichia coli</i> isolated from healthy broiler chickens slaughtered for human consumption in Korea. A total of 332<i> E. coli</i> isolates were identified from 339 cloacal swabs in 2019. More than 90% of the isolates were resistant to multiple antimicrobials. ESBL/pAmpC-production was noted in 14% (46/332) of the isolates. Six of the CTX-M-β-lactamase-producing isolates were found to co-harbor at least one plasmid-mediated quinolone resistance gene. We observed the co-existence of<i> bla</i>_CMY-2 and <i>mcr-1</i> genes in the same isolate for the first time in Korea. Phylogenetic analysis demonstrated that the majority of <i>bla</i>_CMY-2-carrying isolates belonged to subgroup D. Conjugation confirmed the transferability of <i>bla</i>_CTX-M and <i>bla</i>_CMY-2 genes, as well as non-β-lactam resistance traits from 60.9% (28/46) of the ESBL/pAmpC-producing isolates to a recipient <i>E. coli</i> J53. The IS<i>ECP</i>, <i>IS903</i>, and <i>orf477</i> elements were detected in the upstream or downstream regions. The <i>bla</i>_CTX-M and <i>bla</i>_CMY-2 genes mainly belonged to the IncI1, IncHI2, and/or IncFII plasmids. Additionally, the majority of ESBL/pAmpC-producing isolates exhibited heterogeneous PFGE profiles. This study showed that healthy chickens act as reservoirs of ESBL/pAmpC-producing <i>E. coli</i> that can potentially be transmitted to humans.