Combined effect of Trachyspermum ammi essential oil and propolis ethanolic extract on some foodborne pathogenic bacteria

Natural compounds including essential oils (EOs) are used to inhibit the pathogenic bacterial growth in foods. The objective of this study was to investigate the combined effect of Trachyspermum ammi EO and propolis ethanolic extract (PEE) on some food pathogenic bacteria. In this study, the effect of T. ammi EO and PEE at different concentrations, individually and in combination, on Escherichia coli, Salmonella typhimurium, Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus were investigated using minimum inhibitory concentration and fractional inhibitory concentration (FIC) indices. Moreover, the effect of sub-inhibitory concentrations of EO and extract on E. coli and S. aureus growth curve was determined. The results revealed the synergistic effect of T. ammi EO and PEE on S. aureus, B. cereus, E. coli, S. typhimurium, and L. monocytogenes. The effects of EO and extract sub-inhibitory concentrations on bacterial growth curve resulted in an increased lag phase of the culture and decelerated bacterial growth, especially S. aureus. The results showed that T. ammi EO and PEE, especially when combined, are effective in bacterial growth inhibition and their potential use in food systems is recommended.