Evaluation of antibacterial activity and synergistic effect between antibiotic and the essential oils of some medicinal plants

Objective: To demonstrate the in vitro antibacterial properties of five essential oils against ten bacterial strains and study the synergistic effect of the combination of essential oils with standard antibiotics. Methods: Origanum compactum, Chrysanthemum coronarium, Thymus willdenowii Boiss, Melissa officinalis and Origanum majorana L. were used alone and combined used with standard antibiotics to evaluate their antimicrobial activities. The disk diffusion method was employed. Results: The results showed that the combined application of the essential oils of the plants with antibiotics led to a synergistic effect in some cases, but antagonistic effect was also observed in some bacteria. Conclusions: This study shows that the combination of essential oils of the five plants with antibiotics may be useful in the fight against emerging microbial drug resistance.