Antibacterial synergistic and antagonistic effects of commercial essential oils from thymus vulgaris l. and syzygium aromaticum l. in combination with nigella sativa l.

The aim of this study was to assess how Nigella sativa L. (black cumin) essential oil (EO) modify the antibacterial activity of Thymus vulgaris L. (thyme) EO and Syzygium aromaticum L. (clove) EO. We used two bacterial strains Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923. The micro atmosphere assay method was used. The tests were performed after prior incubation at room temperature for 30 and 60 minutes of the mixtures of black cumin EO with thyme EO and clove EO, respectively. After 60 minutes of incubating the mixture of thyme EO: black cumin EO (1:1.54) the maximal antibacterial activity of thyme EO against E. coli was reduced by 50%. Similarly, the RA of the clove EO against E. coli is decreased by 50% when clove EO and black cumin EO are mixed in 1:5.19 ratio. The present study demonstrated that mixture of EOs is not always beneficial.