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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Egg and Poultry Production Safety Research Unit » Research » Publications at this Location » Publication #421179
Research Project: Reduction of Foodborne Pathogens and Antimicrobial Resistance in Poultry Production Environments

Location: Egg and Poultry Production Safety Research Unit

Title: The effects of acidifying agents on the growth, antimicrobial resistance, and plasmid genome of Salmonella Infantis

Author
item Cho, Sohyun
item CHUNG, TAEJUNG - Department Of Energy
item Zock, Gregory
item Oladeinde, Adelumola
item Rothrock Jr, Michael
item Li, Xiang
item Plumblee Lawrence, Jodie
item AL HAKEEM, WALID - Department Of Energy

Submitted to: International Poultry Scientific Forum
Publication Type: Abstract Only
Publication Acceptance Date: 11/20/2024
Publication Date: 1/27/2025
Citation: Cho, S., Chung, T., Zock, G.S., Oladeinde, A.A., Rothrock Jr, M.J., Li, X., Plumblee Lawrence, J.R., Al Hakeem, W. 2025. The effects of acidifying agents on the growth, antimicrobial resistance, and plasmid genome of Salmonella Infantis. (abstract)International Poultry Scientific Forum.

Interpretive Summary:

Technical Abstract: Salmonella Infantis has become one of the main serotypes found in chicken products in the US and across the globe. S. Infantis strains that harbor the pESI plasmid are prevalent in litter samples from broiler farms, indicating that pre-harvest management practices cannot efficiently eradicate S. Infantis. The objective of this study was to evaluate if acidifying agents that are extensively used to acidify litter and water for poultry house ammonia control and pathogen reduction have a deleterious effect on the survival and growth of S. Infantis. We also investigated if there are fitness effects of pESI on S. Infantis when grown in the presence of acidifiers by comparing the plasmid-carrying strains with the plasmid-free strains. When S. Infantis was exposed to sodium bisulfate (SBS) and acidified copper sulfate (ACS) at levels recommended by the manufacturers, there was a bacteriostatic effect, but when exposed to ACS at double the recommended concentration, S. infantis growth was totally suppressed. This suggests that SBS and ACS prepared at the recommended concentrations to be used in the poultry industry do not prevent the growth of Salmonella. When the pESI-positive strains and pESI-negative strains were cultured under various conditions of acidifiers and pH, there were no statistical differences in the maximum growth and lag phase time (P > 0.05), using the Kruskal-Wallis test, followed by Dunn's multiple comparison test, indicating that there was no fitness cost or advantage to a pESI carriage. However, when exposed to SBS at pH of 4, both the strains exhibited reduced growth with a significantly long lag phase time (P < 0.05). In addition, changes in AMR phenotypes and pESI plasmid genome compositions were detected in pESI-carrying isolates; they lost either sulfamethoxazole (SOX) or trimethoprim-sulfamethoxazole (SXT) resistance phenotypes as well as the genes on the plasmid associated with SOX and SXT resistance. The media containing SBS posed a selective pressure on S. Infantis to drop SOX and SXT resistance, and further studies are needed to determine why SOX or SXT resistance and the sul1 or dfrA14 genes were lost in the presence of SBS.