Distribution and transfer of plasmid replicon families among multidrug resistant Enterococcus faecalis and Enterococcus faecium from poultry

Authors: Jackson, Charlene; CHO, SOHYUN - US Department Of Agriculture (USDA); McMillan, Elizabeth; BARRETT, JOHN - Retired ARS Employee; Hiott, Lari; Woodley, Tiffanie; House, Sandra; Frye, Jonathan

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2022
Publication Date: 6/17/2022
Citation: Jackson, C.R., Cho, S., Mcmillan, E.A., Barrett, J.B., Hiott, L.M., Woodley, T.A., House, S.L., Frye, J.G. 2022. Distribution and transfer of plasmid replicon families among multidrug resistant Enterococcus faecalis and Enterococcus faecium from poultry. Microorganisms. https://doi.org/10.3390/microorganisms10061244.
DOI: https://doi.org/10.3390/microorganisms10061244

Interpretive Summary: Plasmids are pieces of DNA separate from the chromosome. They may contain antibiotic resistance genes which can transfer among bacteria. The presence and transfer of plasmids from commensal bacteria, such as Enterococcus, to pathogenic bacteria may contribute to the spread of antibiotic resistance. In this study, occurrence of plasmid groups in antibiotic resistant enterococci from poultry carcass rinses was determined. Transfer of plasmids and antibiotic resistance between enterococci was also tested. Sixteen to 48% of enterococci were positive for at least one plasmid group. Fourteen plasmid groups were detected, and ten plasmid groups were shared among the enterococci. Eight plasmids were transferred between enterococci. Results showed that enterococci from poultry serve as a reservoir of plasmids and antibiotic resistance that can transfer to other bacteria. As enterococci are a leading cause of hospital infections, food safety and health scientists will use this data to determine sources of enterococci containing plasmids and resistance genes and the potential of transfer into the human population through contact with poultry products.

Technical Abstract: The presence and transfer of plasmids from commensal bacteria to more pathogenic bacteria may contribute to dissemination of antimicrobial resistance. However, prevalence of plasmids from commensal bacteria in food animals such as the enterococci remains largely unknown. In this study, diversity and prevalence of plasmid families from multidrug resistant (MDR; resistance to three or more antimicrobials) enterococci from poultry carcasses was determined. Plasmid-positive MDR enterococci were also tested for the ability to transfer plasmids to other enterococci using conjugation. MDR Enterococcus faecalis (n=98) and Enterococcus faecium (n=696) isolated from poultry carcass rinsates between 2004 and 2011 were tested for the presence of 21 plasmid replicon (rep) families using multiplex PCR. Approximately 48% of E. faecalis (47/98) and 16% of E. faecium (110/696) were positive for at least one rep-family. Fourteen rep-families were detected overall, and ten rep-families were shared among E. faecalis and E. faecium. The rep7 and rep17 family were unique to E. faecalis, while rep5 and rep8 families were unique to E. faecium. The rep9 family was predominant among both E. faecalis and E. faecium for all years tested. The greatest number of rep-families detected was in 2005 (n=10) and the least in 2009 (n=1). Eight rep-families were transferred from E. faecalis donors to the E. faecalis JH2-2 recipient using conjugation. Results from this study showed that E. faecalis and E. faecium from poultry carcasses contain numerous and diverse rep-families that are capable of conjugal transfer.