Evaluation of Antimicrobial Activity of Several Medicinal Plants Against Clinically Isolated Staphylococcus aureus from Humans and Sheep

Continuous and indiscriminate use of chemical drugs causes an important phenomenon of resistance to microorganisms. Accordingly, the effect of medications is minimized or offset, increasing drug use and the need to study mixtures with more latest and powerful formulations. On the other hand, it has been reported that many plants essential oils have a significant inhibitory effect on pathogenic microorganisms.

This study aimed to evaluate the antimicrobial activity of some curative herbs against some clinical bacteria of humans and sheep.

The leaves of chicory (Cichorium intybus L.), Hypericum perforatum L., Lavandula angustifolia, Thymus vulgaris L., and Taxus baccata L. were collected and determined in the botanical laboratory of the University of Zabol. Forty grams of dried leaves was used in 400mL of ethanol (96%) to prepare the ethanolic extract. DPPH was used to determine the activity of reactive oxygen species (ROS) trapping. The antimicrobial effects were studied by the disk diffusion (6 mm) method in Müller-Hinton agar medium according to the method by Bauer et al.

The minimum inhibitory concentrations (MICs) of chicory, thyme, H. perforatum, French lavender, and yarrow extracts in human clinical Staphylococcus aureus were 6.25, 12.5, 3.1, 25, and 6.25 ppm, respectively, but, in sheep, clinical S. aureus, were 12.5, 6.25, 3.1, 12.5, and 25 ppm, respectively. The minimum bactericidal concentrations (MBCs) of chicory, thyme, H. perforatum, French lavender, and yarrow extracts in human clinical S. aureus were 12.5, 25, 6.25, 50, and 12.5 ppm, respectively, but, in sheep clinical S. aureus, were 25, 12.5, 6.25, 25, and 50 ppm, respectively. The most effective extract in inhibiting the growth of S. aureus was the H. perforatum L. extract with an 8.9-mm diameter growth inhibition zone.

Regarding the side effects of artificial medications and antimicrobials, as well as the significant influence of healing herb extracts used in this study, it was found that H. perforatum was the most effective plant against S. aureus. It should be noted that plant extracts were more effective in human clinical S. aureus than in sheep clinical S. aureus.