ARS | Publication request: Bactericidal activity of alkaline salts of fatty acids towards bacteria associated with poultry processing

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 6, 2011
Publication Date: September 6, 2011
Citation: Hinton Jr, A., Ingram, K.D. 2011. Bactericidal activity of alkaline salts of fatty acids towards bacteria associated with poultry processing. XXII Latin American Poultry Congress, September 5-9, 2011, Buenos Aires, Argentina. Meeting Proceedings. #156.

Interpretive Summary: The agar diffusion method was used to examine the ability of 5 naturally occurring fatty acids to kill bacteria associated with poultry processing. Tests were performed to compare the ability of the fatty acids to kill pathogenic, spoilage, and indicator bacteria found on processed poultry meat. Mixtures of fatty acids were prepared by dissolving the fatty acids in potassium hydroxide (KOH) solutions and using citric acid to adjust the pH of the solutions to 10.5. The experiments were performed by making small wells in solid agar media that had been inoculated with test bacteria, and filling the wells with fatty acid-KOH solutions. The plates were then incubated to allow the bacteria suspended in the agar to grow. Zones of inhibition of bacterial growth produced around the agar wells by the fatty acid-KOH solutions were measured after incubation. Experimental results showed that caproic acid-KOH inhibited growth of 1 of 8 bacteria; myristic acid inhibited growth 2 of 8 bacteria; caprylic acid inhibited of 3 of 8 bacteria; and capric and lauric acids inhibited growth of all 8 bacterial isolates. Findings from these experiments indicate that several fatty acids can be used to kill bacteria associated with poultry processing. These experiments also showed that the agar diffusion method can be used to quickly screen fatty acid formulations for their ability to kill bacteria.

Technical Abstract: Antibacterial activity of alkaline salts of caproic, caprylic, capric, lauric, and myristic acids were determined using the agar diffusion assay. A 0.5M concentration of each fatty acid (FA) was dissolved in 1.0 M potassium hydroxide (KOH), and pH of the mixtures was adjusted to 10.5 with citric acid. Solutions were filter sterilized by passage through 0.2 µm filters. Sterilized agar media was then inoculated with 106 colony-forming-units/ml of Acinetobacter calcoaceticus, Campylobacter jejuni, Enterococcus faecalis, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium, or Staphylococcus simulans. Wells were made in solidified agar, and 0.1 ml of each fatty acid solution was added to separate wells. Agar plates were incubated for 24-48 h, and zones of inhibition of bacterial growth around the wells on the incubated plates were measured. Results indicated that caproic acid-KOH inhibited growth of C. jejuni only, while caprylic acid-KOH inhibited growth of 3 of the Gram negative isolates, E. coli, P. fluorescens, and C. jejuni. Capric-KOH and lauric acid-KOH exhibited antibacterial activity towards all 8 bacterial isolates, however. Myristic acid-KOH was only inhibitory towards the 2 Gram positive cocci, E. faecalis and S. simulans. Findings demonstrated that alkaline salts of FA-KOH mixtures possess antibacterial activity towards several bacteria associated with poultry processing and that the agar diffusion assay can be used to screen antibacterial activity of these solutions.