Susceptibility of pESI positive Salmonella to treatment with biocide chemicals approved for use in poultry processing as compared to Salmonella without the pESI plasmid

Authors: MCMILLAN, ELIZABATH - Oak Ridge Institute For Science And Education (ORISE); Adams, Eric; Mitchell, Trevor; Hawkins, Jaci; Read, Quentin; Pokoo-Aikins, Anthony; Meinersmann, Richard - Rick; HARRIS, CAITLIN - Oak Ridge Institute For Science And Education (ORISE); Hughes Jr, Michael; Glenn, Anthony - Tony; Berrang, Mark

Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2024
Publication Date: 7/10/2024
Citation: Mcmillan, E., Adams, E.S., Mitchell, T.R., Hawkins, J.A., Read, Q.D., Pokoo-Aikins, A., Meinersmann, R.J., Harris, C., Hughes Jr, M.D., Glenn, A.E., Berrang, M.E. 2024. Susceptibility of pESI positive Salmonella to treatment with biocide chemicals approved for use in poultry processing as compared to Salmonella without the pESI plasmid. Letters in Applied Microbiology. https://doi.org/10.1093/lambio/ovae067.
DOI: https://doi.org/10.1093/lambio/ovae067

Interpretive Summary: Humans can be infected with Salmonella by eating contaminated chicken meat. The Food Safety and Inspection Service tests meat in processing plants and finds that around 4% is contaminated with Salmonella. Infantis is one of the most common serotypes of Salmonella they find on chicken and turkey meat when Salmonella is detected. The recent increase in recovery of Infantis has been explained by the pESI plasmid, an extra piece of DNA which the majority of Infantis isolates carry. This plasmid contains genes that give the Salmonella cells carrying it fitness advantage over Salmonella which don’t carry it, including resistance to certain sanitizers, like hydrogen peroxide. Because this strain is so common among Salmonella isolates from poultry meat, we sought to determine the susceptibility of this strain to sanitizers used in poultry processing. We found that isolates carrying pESI were not more tolerant or susceptible to treatment with peracetic acid, cetylpiridinium chloride, calcium hypochlorite, or sodium hypochlorite than Salmonella cells without this plasmid. This was true when cultures were treated to simulate two types of sanitization common in processing plants: exposed directly to the chemicals for 15 seconds to simulate a spray wash with the chemicals and 90 minutes to simulate the immersion of chicken meat in chill tanks which contain the chemicals. This work emphasized the importance of investigating tolerance to sanitizers on meat products in an application similar to how the sanitizer is applied in a processing plant.

Technical Abstract: Salmonella is a common cause of human foodborne illness which is frequently associated with consumption of contaminated or undercooked poultry meat consumption. Serotype Infantis is among the most common serotypes isolated from poultry products. Isolates of serotype Infantis carrying the pESI plasmid have been shown to exhibit oxidizer tolerance. Therefore, sixteen strains of Salmonella with and without pESI carriage were investigated for susceptibility to biocide chemical processing aids approved for use in U.S. poultry processing. All strains tested were susceptible to all concentrations of peracetic acid, cetylpiridinium chloride, and sodium hypochlorite when applied for 90 minutes. When cetylpiridinium chloride, calcium hypochlorite, and sodium hypochlorite were applied for 15 seconds to simulate spray time, strains responded similarly to each other. However, strains responded variably to exposure to PAA. The variation was not statistically significant and appears unrelated to pESI carriage. Results highlight the necessity of testing biocide susceptibility in the presence of organic material and in relevant in situ applications.