Antimicrobial activity of clove and rosemary essential oils alone and in combination

In the present study, the antimicrobial activity of the essential oils from clove (Syzygium aromaticum (L.) Merr. et Perry) and rosemary (Rosmarinus officinalis L.) was tested alone and in combination. The compositions of the oils were analysed by GC/MS. Minimum inhibitory concentrations (MIC) against three Gram‐positive bacteria, three Gram‐negative bacteria and two fungi were determined for the essential oils and their mixtures. Furthermore, time‐kill dynamic processes of clove and rosemary essential oils against Staphylococcus epidermidis, Escherichia coli and Candida albicans were tested. Both essential oils possessed significant antimicrobial effects against all microorganisms tested. The MICs of clove oil ranged from 0.062% to 0.500% (v/v), while the MICs of rosemary oil ranged from 0.125% to 1.000% (v/v). The antimicrobial activity of combinations of the two essential oils indicated their additive, synergistic or antagonistic effects against individual microorganism tests. The time‐kill curves of clove and rosemary essential oils towards three strains showed clearly bactericidal and fungicidal processes of ¹/₂ × MIC, MIC, MBC and 2 × MIC. Copyright © 2007 John Wiley & Sons, Ltd.