Inhibition and interactions of Campylobacter jejuni from broiler chicken houses with organic acids

Authors: Beier, Ross; Byrd Ii, James - Allen; Caldwell, Denise; Andrews, Kathleen - Kate; Crippen, Tawni - Tc; Anderson, Robin; Nisbet, David

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2019
Publication Date: 7/30/2019
Publication URL: https://handle.nal.usda.gov/10113/6605031
Citation: Beier, R.C., Byrd II, J.A., Caldwell, D.Y., Andrews, K., Crippen, T.L., Anderson, R.C., Nisbet, D.J. 2019. Inhibition and interactions of Campylobacter jejuni from broiler chicken houses with organic acids. Microorganisms. 7(8):1-18. https://doi.org/10.3390/microorganisms7080223.
DOI: https://doi.org/10.3390/microorganisms7080223

Interpretive Summary: Organic acids are commonly used as a carcass wash to remove bacterial loads from animal carcasses during food production. In this study, the interactions of six organic acids with 96 Campylobacter jejuni (C. jejuni) strains obtained from broiler chicken houses were studied. The pH was determined at the molar minimum inhibitory concentrations (MICMs) of the C. jejuni strains and, using the determined pH, the concentrations of the undissociated and dissociated organic acids were calculated using the Henderson-Hasselbalch equation at the MICMs for the C. jejuni strains. Since all C. jejuni strains behaved somewhat different to each organic acid, the results of the C. jejuni obtained from each individual organic acid – acetic, butyric, citric, formic, lactic, and propionic acid - were treated as a single group for each organic acid. It was determined that bacterial inhibition was not solely dependent on pH or on the undissociated organic acid species, but C. jejuni inhibition was more closely correlated with the dissociated organic acid species. A small drop in the concentration of the dissociated organic acids may result in bacteria escaping disinfection. Therefore, an organic acid carcass wash may not provide the expected elimination of surface bacteria if the concentration of the dissociated organic acid is not carefully controlled. Citric acid appeared to be the best organic acid to inhibit C. jejuni.

Technical Abstract: Campylobacter jejuni (C. jejuni) is a bacterial species that is a major cause of diarrheal disease worldwide and is among the top 5 foodborne pathogens in the United States. Organic acids (OAs) are often used during food production to remove bacteria from animal carcasses. The interactions of six OAs with 96 C. jejuni strains obtained from shoe covers used in broiler chicken houses at different poultry farms in several states were studied by determining the molar minimum inhibitory concentrations (MICMs) of the C. jejuni strains and the pH values at the MICMs. The undissociated and dissociated OA concentrations were calculated at the MICMs of the C. jejuni strains using the Henderson-Hasselbalch equation. The results for the 96 C. jejuni strains were treated as a single group for each different OA. Inhibition of C. jejuni was not dependent on pH or on the undissociated OA species, but C. jejuni inhibition correlated with the dissociated OA species. Therefore, if the concentration of a dissociated OA decreases from optimum, it is then expected that C. jejuni bacteria would escape disinfection. A carcass wash using OAs should have the dissociated OA concentration carefully controlled. We suggest maintaining a concentration of the dissociated acetic, butyric, citric, formic, L-lactic, and propionic acids at 25, 23, 21, 36, 20, and 24 mM, respectively, when using a carcass wash with these OAs to remove 97% or more of the C. jejuni bacteria studied here. However, due to C. jejuni utilization of acetate, butyrate, formate, L-lactate, and propionate, these five OAs may not be the best choice to use for a carcass wash to remove C. jejuni contamination. Of the six OAs, dissociated citric and L-lactic acid were the most efficient at inhibiting C. jejuni.