Antimicrobial activity of essential oils of cultivated oregano (Origanum vulgare), sage (Salvia officinalis), and thyme (Thymus vulgaris) against clinical isolates ofEscherichia coli,Klebsiella oxytoca, andKlebsiella pneumoniae

Abstract

BackgroundOregano (Origanum vulgare), sage (Salvia officinalis), and thyme (Thymus vulgaris) are aromatic plants with ornamental, culinary, and phytotherapeutic use all over the world. In Europe, they are traditionally used in the southern countries, particularly in the Mediterranean region. The antimicrobial activities of the essential oils (EOs) derived from those plants have captured the attention of scientists as they could be used as alternatives to the increasing resistance of traditional antibiotics against pathogen infections. Therefore, significant interest in the cultivation of various aromatic and medicinal plants is recorded during the last years. However, to gain a proper and marketable chemotype various factors during the cultivation should be considered as the geographical morphology, climatic, and farming conditions. In this frame, we have studied the antimicrobial efficiency of the EOs from oregano, sage, and thyme cultivated under different conditions in a region of NE Greece in comparison to the data available in literature.MethodsPlants were purchased from a certified supplier, planted, and cultivated in an experimental field under different conditions and harvested after 9 months. EOs were extracted by using a Clevenger apparatus and tested for their antibacterial properties (Minimum inhibitory concentration – MIC) against clinical isolates of multidrug resistant Escherichia coli (n=27), Klebsiella oxytoca (n=7), and Klebsiella pneumoniae (n=16) strains by using the broth microdilution assay.ResultsOur results showed that the most sensitive organism was K. oxytoca with a mean value of MIC of 0.9 µg/mL for oregano EOs and 8.1 µg/mL for thyme. The second most sensitive strain was K. pneumoniae with mean MIC values of 9.5 µg/mL for thyme and 73.5 µg/mL for oregano EOs. E. coli strains were among the most resistant to EOs antimicrobial action as the observed MICs were 24.8–28.6 µg/mL for thyme and above 125 µg/mL for thyme and sage. Most efficient were the EOs from thyme followed by those of oregano.ConclusionsWith MIC values above 150 µg/mL, sage EOs did not show any antibacterial efficiency against the majority of the strains. However, no significant differences were observed concerning the antimicrobial action of all EOs originating from irrigated versus non-irrigated cultivated aromatic plants.

The effect of different preparation methods on the development of chitosan/thyme oil/montmorillonite nanocomposite active packaging films

“…The MIC and the MBC values were both determined at 0.3 mg TO/ml liquid culture. Our results are in accordance with other published papers that also reported an increased antibacterial action of TO with the MIC values ranged between 0.25 and 0.4 mg/ml for E. coli (Fournomiti et al, ; Pei, Zhou, Ji, & Xu, ).…”

Chemical composition and antioxidant activities of essential oils from different parts of the oregano

“…In recent years, many reports have shown that oregano oil has strong antioxidant activities (Gilling et al, 2014;Bhargava et al, 2015;Fournomiti et al, 2015) and is a strong candidate to replace synthetic antioxidants used in the industry (Stuessy, 2009;Céspedes et al, 2013). Rosemary acid ester, which can be obtained from oregano oils, has strong antioxidant effects (Mechergui et al, 2010).…”

Pharmacological and Phytochemical Studies of Origanum Vulgare: A Review

“…Champawat (1840 m); and 7. Almora (2220 m) [17]. O. vulgare can also be found in other places like Portugal, Spain, Afghanistan, China, Nepal, Pakistan, Denmark and also in Europeon parts of Russia [18].…”