Bacteria Broadly-Resistant to Last Resort Antibiotics Detected in Commercial Chicken Farms

• Main Authors: Jared M. Jochum, Graham A. J. Redweik, Logan C. Ott, Melha Mellata
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Microorganisms
• Subjects: ESBL-producing <i>Enterobacteriaceae</i>; colistin resistant <i>Escherichia coli</i>; carbapenem-resistant <i>Acinetobacter</i>; hens; maturity stages; plasmid
• Online Access: https://www.mdpi.com/2076-2607/9/1/141

Resistance to last resort antibiotics in bacteria is an emerging threat to human and animal health. It is important to identify the source of these antimicrobial resistant (AMR) bacteria that are resistant to clinically important antibiotics and evaluate their potential transfer among bacteria. The objectives of this study were to (i) detect bacteria resistant to colistin, carbapenems, and β-lactams in commercial poultry farms, (ii) characterize phylogenetic and virulence markers of <i>E. coli</i> isolates to potentiate virulence risk, and (iii) assess potential transfer of AMR from these isolates via conjugation. Ceca contents from laying hens from conventional cage (CC) and cage-free (CF) farms at three maturity stages were randomly sampled and screened for extended-spectrum β-lactamase (ESBL)-producing <i>Enterobacteriaceae</i>, carbapenem-resistant <i>Acinetobacter</i> (CRA), and colistin resistant <i>Escherichia coli</i> (CRE) using CHROMagar™ selective media. We found a wide-spread abundance of CRE in both CC and CF hens across all three maturity stages. Extraintestinal pathogenic <i>Escherichia coli</i> phylogenetic groups B2 and D, as well as plasmidic virulence markers <i>iss</i> and <i>iutA</i>, were widely associated with AMR <i>E. coli</i> isolates. ESBL-producing <i>Enterobacteriaceae</i> were uniquely detected in the early lay period of both CC and CF, while multidrug resistant (MDR) <i>Acinetobacter</i> were found in peak and late lay periods of both CC and CF. CRA was detected in CF hens only. <i>bla_CMY</i> was detected in ESBL-producing <i>E. coli</i> in CC and CF and MDR <i>Acinetobacter</i> spp. in CC. Finally, the <i>bla_CMY</i> was shown to be transferrable via an IncK/B plasmid in CC. The presence of MDR to the last-resort antibiotics that are transferable between bacteria in food-producing animals is alarming and warrants studies to develop strategies for their mitigation in the environment.