Inhibition of Listeria monocytogenes by Food Antimicrobials Applied Singly and in Combination
Article first published online: 3 NOV 2010
© 2010 Institute of Food Technologists®
Journal of Food Science
Volume 75, Issue 9, pages M557–M563, November/December 2010
How to Cite
Brandt, A. L., Castillo, A., Harris, K. B., Keeton, J. T., Hardin, M. D. and Taylor, T. M. (2010), Inhibition of Listeria monocytogenes by Food Antimicrobials Applied Singly and in Combination. Journal of Food Science, 75: M557–M563. doi: 10.1111/j.1750-3841.2010.01843.x
- Issue published online: 3 NOV 2010
- Article first published online: 3 NOV 2010
- MS 20100420 Submitted 4/16/2010, Accepted 7/31/2010.
- in vitro;
- Listeria monocytogenes;
- ready-to-eat meat;
Abstract: Combining food antimicrobials can enhance inhibition of Listeria monocytogenes in ready-to-eat (RTE) meats. A broth dilution assay was used to compare the inhibition of L. monocytogenes resulting from exposure to nisin, acidic calcium sulfate, ɛ-poly-L-lysine, and lauric arginate ester applied singly and in combination. Minimum inhibitory concentrations (MICs) were the lowest concentrations of single antimicrobials producing inhibition following 24 h incubation at 35 °C. Minimum bactericidal concentrations (MBCs) were the lowest concentrations that decreased populations by ≥3.0 log10 CFU/mL. Combinations of nisin with acidic calcium sulfate, nisin with lauric arginate ester, and ɛ-poly-L-lysine with acidic calcium sulfate were prepared using a checkerboard assay to determine optimal inhibitory combinations (OICs). Fractional inhibitory concentrations (FICs) were calculated from OICs and were used to create FIC indices (FICIs) and isobolograms to classify combinations as synergistic (FICI < 1.00), additive/indifferent (FICI= 1.00), or antagonistic (FICI > 1.00). MIC values for nisin ranged from 3.13 to 6.25 μg/g with MBC values at 6.25 μg/g for all strains except for Natl. Animal Disease Center (NADC) 2045. MIC values for ɛ-poly-L-lysine ranged from 6.25 to 12.50 μg/g with MBCs from 12.50 to 25.00 μg/g. Lauric arginate ester at 12.50 μg/g was the MIC and MBC for all strains; 12.50 mL/L was the MIC and MBC for acidic calcium sulfate. Combining nisin with acidic calcium sulfate synergistically inhibited L. monocytogenes; nisin with lauric arginate ester produced additive-type inhibition, while ɛ-poly-L-lysine with acidic calcium sulfate produced antagonistic-type inhibition. Applying nisin along with acidic calcium sulfate should be further investigated for efficacy on RTE meat surfaces.
Practical Application: This study demonstrates the potential for combinations of antimicrobials to result in greater pathogen inhibition as compared to the application of a single antimicrobial. The data presented in this study can aid the food industry in developing more efficient and effective application of antimicrobials. These findings should also prompt further studies validating the inhibitory effect of combinations of antimicrobials on ready-to-eat surfaces.