Evaluation of Antimicrobials Against Multi-strain Cocktails of Salmonella, Escherichia Coli O157:h7 and Listeria Monocytogenes Using a Kinetic Growth Inhibition Assay

Abstract

The objective of this work was to evaluate the effect of antimicrobials that are commercially available for the food industry using a kinetic growth assay. The antimicrobials used in our study were tested to evaluate various concentrations in head-to-head trials against multi-strain cocktails of Salmonella, E. coli O157:H7, and L. monocytogenes. We also determined the Minimum Inhibitory Concentration (MIC). Mixed strains <&ldquo>"cocktails"<&rdquo> were prepared comprising either 6 strains of Salmonella, 4 strains of E. coliO157:H7, and 5 strains of L. monocytogenes which were separately cultured using TSB broth and used to inoculate antimicrobials performed in 96-well flat bottom microplates. The microplates were incubated using the Tecan GENious<super>TM </super> microplate reader using Magellan data analysis software to obtain growth curves at different concentrations of the antimicrobials. Measurements were taken as optical density (OD_595nm) readings every 30 minutes up to 48 hours. The following antimicrobials were tested against Salmonella,E. coliO157:H7, and L. monocytogenes with their respective results as Minimum Inhibitory Concentration (MIC): acetic acid (4%, 4% and 4%), Aftec (1.25%, 1.25% and 1.25%), AvGard XP (0.75%, 0.75% and 0.75%), citric acid (0.5%, 0.5% and 0.5%), Cytoguard (2.5%, 2.5% and 1.25%), lactic acid (0.5%, 0.5% and 0.25%), Protect M (0.07%, 0.07% and 0.04%), peroxyacetic acid (0.063%, 0.063% and 0.125%), PuraQ XTend (0.5%, 0.25% and 0.016%), and Syntrx 3300 (2%, 2% and 2%). The data identifies the MIC levels of antimicrobial that gives complete inhibition of the various pathogen cocktail mixtures. Our research suggests that, the levels of the various antimicrobials may be used to inhibit pathogen growth and be beneficial for consumers.