AUTHOR=Bythwood Tameka N. , Soni Vivek , Lyons Karen , Hurley-Bacon Anne , Lee Margie D. , Hofacre Charles , Sanchez Susan , Maurer John J. 

TITLE=Antimicrobial Resistant Salmonella enterica Typhimurium Colonizing Chickens: The Impact of Plasmids, Genotype, Bacterial Communities, and Antibiotic Administration on Resistance

JOURNAL=Frontiers in Sustainable Food Systems

VOLUME=3

YEAR=2019

URL=https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2019.00020

DOI=10.3389/fsufs.2019.00020

ISSN=2571-581X

ABSTRACT=<p>The rise in <italic>Salmonella</italic> resistance to cephalosporins and fluoroquinolones has become a significant threat to public health. At issue, is whether agricultural use of antimicrobials is selecting antibiotic resistance in <italic>Salmonella</italic> and the degree to which large antimicrobial resistance gene reservoirs, present in animal manures, contribute to this resistance. Two <italic>in vivo</italic> studies were performed to address these questions. In the first study, chickens were administered <italic>Salmonella</italic> and commensals, including an <italic>Escherichia coli</italic> strain with a mobile, ceftiofur-resistance plasmid, in order to determine how antibiotic administration impacted resistance in <italic>E. coli</italic> and <italic>Salmonella</italic>. All antibiotics administered to chickens increased streptomycin resistance in <italic>E. coli</italic>. However, only ceftiofur administration increased resistance in <italic>Salmonella</italic> and specifically to extended-spectrum β-lactams and cephalosporins (ESBL). There was no significant increase in ESBL-resistant <italic>Salmonella</italic> in chickens administered a ceftiofur-resistance plasmid donor. In the second study, chickens were administered two different isolates of <italic>S. enterica</italic> Typhimurium and a chicken resistome to serve as a gene donor. Birds were subsequently administered chlortetracycline or streptomycin. Antimicrobial administration significantly altered aminoglycoside and tetracycline resistance in the <italic>Enterobacteriaceae</italic> population. However, there was no significant increase in antimicrobial resistant <italic>Salmonella</italic>. Administration of a chicken resistome had no significant impact on prevalence of resistance in <italic>Enterobacteriaceae</italic> populations, including <italic>Salmonella</italic>. Evident, from both studies, was that these treatments had minimal effect on increasing the prevalence of resistance in <italic>Salmonella</italic>, suggesting that other factors may be more important in dissemination of antimicrobial resistant <italic>Salmonella</italic> in chickens.</p>