Interactions of organic acids with Campylobacter coli from swine

Authors: Beier, Ross; Harvey, Roger; Hernandez, Charles; Hume, Michael; Andrews, Kathleen - Kate; Droleskey, Robert - Bob; DAVIDSON, MAUREEN - Us Food & Drug Administration (FDA); BODEIS-JONES, SONIA - Us Food & Drug Administration (FDA); YOUNG, SHENIA - Us Food & Drug Administration (FDA); Duke, Sara; Anderson, Robin; Crippen, Tawni - Tc; Poole, Toni; Nisbet, David

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2018
Publication Date: 8/10/2018
Citation: Beier, R.C., Harvey, R.B., Hernandez Jr, C.A., Hume, M.E., Andrews, K., Droleskey, R.E., Davidson, M.K., Bodeis-Jones, S., Young, S., Duke, S.E., Anderson, R.C., Crippen, T.L., Poole, T.L., Nisbet, D.J. 2018. Interactions of organic acids with Campylobacter coli from swine. PLoS One. 13(8):e0202100. https://doi.org/10.1371/journal.pone.0202100.
DOI: https://doi.org/10.1371/journal.pone.0202100

Interpretive Summary: Acids such as those produced from a variety of natural biological processes are called organic acids. These organic acids are commonly applied as sprays to carcasses during processing to help kill and remove dangerous foodborne pathogenic bacteria such as E. coli, Salmonella and Campylobacter. In this study, the interactions of six organic acids with over 100 different Campylobacter strains that were obtained previously from live pigs and pork food products were studied. We found that some organic acids were more potent than others, with citric acid being the most potent and formic acid being the least potent, with acids such as lactic, butyric, propionic, and acetic acid being in between in potency. We also found that the antimicrobial effect of the acids was indirectly affected by the pH they were exposed to as this changed their reactivity against the Campylobacter and thus the conditions at which the organic acids are to be applied must be carefully controlled. These results provide useful information to food processors on how to optimize their pathogen control strategies so that they can continue to produce safe and wholesome food for the American consumer.

Technical Abstract: Campylobacter coli is a bacterial species associated with human foodborne illness. Organic acids are commonly used as a carcass wash to remove bacterial loads during food production. In this study, the interactions of six organic acids with 111 C. coli strains obtained from swine and pork food products were studied. The pH was determined at the molar MICs (MICms) of the C. coli strains. The concentrations of the undissociated and dissociated organic acids were calculated using the Henderson-Hasselbalch equation at the MICms of the C. coli strains. Since all C. coli strains behaved similarly to the different organic acids, the results of the C. coli obtained from different locations or environments were treated as a single group for each organic acid, acetic, butyric, citric, formic, lactic, and propionic acid. Bacterial inhibition was not solely dependent on pH or on the undissociated organic acid species, but was more closely correlated with the dissociated organic acid species. A small drop in the concentration of the dissociated organic acids may result in a large number of bacteria escaping disinfection. Therefore, an organic acid carcass wash may not provide the expected elimination of surface bacteria if the concentration of dissociated organic acid is not carefully controlled. We suggest maintaining a concentration of the dissociated acetic, butyric, citric, formic, lactic, and propionic acids of 29, 23, 11, 35, 22, and 25 mM, respectively, when carrying out a carcass wash with these organic acids to remove C. coli strains. However, due to the utilization of acetate, formate, lactate, and propionate by C. coli, these four organic acids may not be the best choice to use for a carcass wash to remove C. coli contamination.