Antibacterial Efficacy of Commercially Available Essential Oils Tested Against Drug-Resistant Gram-Positive Pathogens

Stefanos Petsios,George Mpekoulis,Panagiota Gousia,Hercules Sakkas,Afrodite Ilia,Vangelis Economou,Petros Bozidis,Vasilios Sakkas,Chrissanthy Papadopoulou

doi:10.3390/app8112201

Stefanos Petsios, George Mpekoulis + Show 7 more

Open Access

https://doi.org/10.3390/app8112201

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Abstract

The potential antibacterial activity of basil (Ocimum basilicum), chamomile (Matricaria chamomilla), origanum (Thymus capitatus), tea tree (Melaleuca alternifolia) and thyme (Thymus vulgaris) essential oils, was investigated against 29 Gram-positive bacterial strains isolated from wastewater treatment plants, clinical samples (n = 25) and American Type Culture Collection (ATCC) reference strains (n = 4). Wild bacterial strains included methicillin-resistant Staphylococcus aureus (n = 16) and vancomycin-resistant Enterococcus spp. (n = 9). The antimicrobial activity of the selected oils was studied using the broth macrodilution method. The Minimal Inhibitory Concentration (MIC) values for S. aureus ranged from 0.06 to 0.5% (v/v) for origanum oil, 0.06 to 1% (v/v) for thyme oil, 0.12 to 1% (v/v) for tea tree oil, 0.25 to 4% (v/v) for basil oil and 2 to >4% (v/v) for chamomile oil. For enterococci the MIC values were significantly higher ranging from 0.25 to 1% (v/v), 0.5 to 2% (v/v), 1 to 4% (v/v), 4 to >4% (v/v) and >4% (v/v) for the above-mentioned oils, respectively. The main compounds of the tested essential oils were: estragole (Ocimum basilicum), bisabolol and trans-b-farnesene (Matricaria chamomilla), carvacrol and thymol (Thymus capitatus), terpinen-4-ol and p-cymene (Melaleuca alternifolia), thymol, linalool, and p-cymene (Thymus vulgaris). Origanum essential oil yielded the best antimicrobial results followed by thyme, tea tree, and basil oil, while chamomile oil exhibited weak antibacterial properties.

Highlights

Medicinal plants have been used, since the Hippocrates era, for healing a wide range of diseases including infectious, systematic and inflammatory diseases [1,2]
The appearance of drug-resistance leads to decrease of the existing therapeutic options implying the urgency for the development of new antimicrobials [35]
For centuries it has been well acknowledged the potential of medicinal plants to produce a wide range of phytochemicals, mostly alkaloids, phenolic compounds, polyacetylenes and polypeptides [2,35,41]

Summary

Introduction

Medicinal plants have been used, since the Hippocrates era, for healing a wide range of diseases including infectious, systematic and inflammatory diseases [1,2]. In contrast the current antimicrobial drugs are used for the treatment of human and animal infections for just less than a century [3,4,5]. Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), Streptococcus pneumoniae, Mycobacterium tuberculosis, Enterobacteriaceae producing extended spectrum b-lactamases (ESBLs) and carbapenemases, multidrug-resistant isolates causing severe hospital infections in immunocompromised individuals such as Pseudomonas aeruginosa and Acinetobacter baumannii are increasingly reported from both the human and veterinary medicine practice and the aquatic environment as well [4,7,8,9,10,11,12,13,14]

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