Antimicrobial activity of four essential oils extracted from plants commonly used in traditional medicine against some clinical strains



Introduction: Recently, efforts regarding the discovery of the effectual components of plants possessing antimicrobial properties are advanced. Herbal essential oils are widely used for treatment of various diseases, and they play an important role in healthcare considerations. Objective: This study aims to evaluate the effectiveness of Cinnamomum verum, Eucalyptus globulus, Lavandula angustifolia and Mentha pulegium essential oils against Candida albicans and some pathogenic bacteria. Methods: The antibacterial activity of four essential oils (EOs) against different microbial strains was evaluated using the disk diffusion method as well as determination of the minimal inhibitory concentration (MIC), and bactericidal concentration (MBC). For Candida albicans, the MFC of the plant oils was determined using a macro broth dilution assay. A range of concentrations (50 to 0.2 mg/ml) were prepared in Mueller Hinton Broth medium in flasks. Tween 80 (0.01% v/v) was included to enhance oil solubility. Each flask was inoculated with 108 CFU/ml of C. albicans. The flasks were incubated at 35°C for 48 hours. From each flask 13 μl of culture was inoculated onto Mueller-Hinton Agar plates and incubated at 35°C for 48 h. The plates were observed and the MFC was determined as the lowest concentration of plant oil completely inhibiting the growth of C. albicans. Results: The obtained results showed that all bacteria and yeasts tested were sensitive to cinnamon essential oil with an inhibition zone ranging from 22 to 39.33 mm and a MIC ranging from 0.20 mg/ml to 1.56 mg/ml. At low concentrations ranging from 0.2 to 3.13 mg/ml, this essential oil has shown the most important bactericidal effect. Eucalyptus essential oil showed the highest inhibitory effect on Staphylococcus aureus with a diameter of 21.33±1.15 mm. The antibacterial effect of mint indicates that the most sensitive bacterium is A. boumannii. However, S. enteritidis, C. albicans, K. pneumoni and P. aeruginosa are resistant germs whose inhibition diameter varies from 7.33±1.15 mm to 11.33±1.15 mm. Lavender EO has an inhibitory effect against S. aureus (20.67±1.15 mm) and an intermediate effect against Streptococcus pyogenes, Serratia marcescens and Enterococcus faecalis. Conclusions: The antibacterial activity of essential oils, especially those of cinnamon against the strains studied, supports their potential use as a remedy against infectious microbial diseases.
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