Antimicrobial interactions between essential oil of Stachys lavandulifolia Vahl., with nisin and glycine on foodborne pathogens and food spoilage organisms

Combination of antimicrobial agents can enhance the inhibition of foodborne pathogens and food spoilage organisms. The aim of the study was to evaluate the antimicrobial activity of Stachys lavandulifolia Vahl. essential oil in combination with nisin or glycine, in order to find synergism, indifferent or antagonism interactions. The essential oil of plant was obtained by a clevenger-type apparatus. In order to determine chemical composition, the volatile oil was injected to a GC followed by GC/MS. Antimicrobial properties of the oil, nisin and glycine were determined by a microbroth dilution method, separately. Antimicrobial interactions were carried out using a Checkerboard titration and Fractional Inhibitory Concentration Indices (FICI) were calculated, consequently. Linalool was the most abundant constituent among the oil constituents. The gram negative bacteria and the yeasts were the most resistant and sensitive against glycine and essential oil, respectively. Listeria monocytogenes was the most sensitive and Candida albicans and gram negatives were the most resistant against nisin. Nisin and oil combination resulted in a synergism effect, but the glycine and oil combination led to antagonism, indifferent or additive effects. Antimicrobial interaction of essential oil of Stachys with nisin or glycine resulted in decrease of minimum inhibitory concentrations that was more important for gram negative bacteria and yeasts inhibition. However, minimizing the minimum inhibitory concentrations lonely isn’t equal to a synergism effect and may conclude additive, indifferent or antagonism effects.