Antimicrobial activity of essential oils and structurally related synthetic food additives towards selected pathogenic and beneficial gut bacteria

Aims: To assess the potential of essential oils and structurally related synthetic food additives in reducing bacterial pathogens in swine intestinal tract. Methods and Results: The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Among 66 essential oils/compounds that exhibited >= 80% inhibition towards Salmonellatyphimurium DT104 and Escherichia coli O157:H7, nine were further studied. Most of the oils/compounds demonstrated high efficacy against S. typhimurium DT104, E. coli O157:H7, and E. coli with K88 pili with little inhibition towards lactobacilli and bifidobacteria. They were also tolerant to the low pH. When mixed with pig cecal digesta, these oils/compounds retained their efficacy against E. coli O157:H7. In addition, they significantly inhibited E. coli and coliform bacteria in the digesta, but had little effect on the total number of lactobacilli and anaerobic bacteria. Conclusions: Some essential oils/compounds demonstrated good potential, including efficacy, tolerance to low pH, and selectivity towards bacterial pathogens, in reducing human and animal bacterial pathogens in swine intestinal tract. Significance and Impact of the Study: This study has identified candidates of essential oils/compounds for in vivo studies to develop antibiotic substitutes for the reduction of human and animal bacterial pathogens in swine intestinal tract.