Happy beef: The development of beta-phenylethylamine as a novel nutrient treatment reducing bacterial cell count by Escherichia coli O157:H7 on beef meat

Since its emergence in 1980s, Escherichia coli O157:H7 has often been associated with the consumption of contaminated meat. E. coli O157:H7 continues to persist as a food borne pathogen not only in beef but many other food products as well. One of the reasons for its persistence is its ability to overcome many of the current control effort including citric acid treatments. This research looks at the use of nutrients as a novel way to control E. coli O157:H7. In this research we used Phenotype MicroArray™ technology from BioLog (Hayward, CA) technology to screen 95 carbon and 95 nitrogen nutrient sources for their ability to reduce respiration, biofilm amounts and cell number. The top eight performing nutrients were then screened a second time to look at the effects of concentration on their ability to reduce biomass, biofilm amounts and cell number in beef broth. The second screening allowed for the calculation of the concentrations needed to inhibit these factors by 50%. This screening reduced the number of chemicals from eight to two chemicals, acetoacetic acid and β-phenylethylamine, both of which were characterized by low inhibitory concentrations (<10 mg/ml). In a final experiment, these two chemicals were used in various concentrations as treatment on beef, which was then inoculated with E. coli O157:H7. Only β-phenylethylamine was able to reduce the bacterial cell counts of E. coli O157:H7 over the seven day incubation period. β-phenylethylamine, a natural trace amine found in chocolate after fermentation, was able to reduce the recovered colony forming units by >74%. This shows that a nutrient can be used as a novel way to control phenotypic traits in E. coli O157:H7 in a preventative manner.