Antimicrobial Activity of Essential Oils Evaluated In Vitro against Escherichia coli and Staphylococcus aureus

Abstract

The spread of extended-spectrum β-lactamase-producing Escherichia coli and methicillin-resistant Staphylococcus aureus has caused a reduction in antibiotic effectiveness and an increase in mortality rates. Essential oils (EOs), known for their therapeutic efficacy, can be configured as novel broad-spectrum biocides. Accordingly, the bacteriostatic–bactericidal activity of Citrus Lemon (LEO), Pinus Sylvestris (PEO), Foeniculum Vulgaris (FEO), Ocimum Basilicum (BEO), Melissa Officinalis (MEO), Thymus Vulgaris (TEO), and Zingiber Officinalis Rosc. (GEO), at concentrations ranging from 1.25 to 40% (v/v), were tested in vitro against different E. coli and S. aureus strains using minimal inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). The chemical compositions of the EOs were analyzed using GC/MS. The major components of all seven tested oils were limonene, α-pinene, anethole, estragole, citral, thymol, and zingiberene, respectively. We found that the bacteriostatic–bactericidal activity of the EOs was related to their chemotypes and concentrations, as well as the strain of the bacteria. A dose–effect correlation was found when testing GEO against S. aureus strains, whilst FEO was found to have no activity regardless of concentration. PEO, MEO, and BEO were found to have bactericidal effect with a MIC and MBC of 1.25% (v/v) against S. aureus strains, and LEO was found to have values of 1.25% (v/v) and 5% (v/v) against ATCC and clinical isolate, respectively. Interestingly, the antimicrobial activity of TEO was not related to oil concentration and the complete inhibition of growth across all E. coli and S. aureus was observed. Although preliminary, our data demonstrate the efficacy of EOs and pave the way for further investigations on their potential synergistic use with traditional drugs in the human and veterinary fields.

Invitroanti-Staphylococcus aureusactivity of the methanol extract from Mitrephora thoreliiPierre’s branches and leavesin Lam Dong Province, Viet Nam

“…In this instance, the extract from Mitrephora thorelii should be noted for its bactericidal properties. [18,20]. Many experimental studies have shown a correlation between the antibacterial activity of plant extracts and secondary compounds found in plants [22].…”

Natural Emulsions Based on Essential Oils as Antifungal and Antimycotoxicogenic Agents on Wheat for Bakery Industry

“…In previous papers regarding the antifungal and antimycotoxicogenic potential of individual EOs of coriander, thyme, and oregano, it was highlighted the contribution of thymol and o-cymene as the major components in thyme EO, linalool in coriander EO, and carvacrol and o-cymene in oregano EO [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. Other minor compounds, such as caryophyllene, β-myrcene, p -cymene, and γ-terpinene, were identified in the three analysed EOs [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

Pilot Study on the Action of Thymus vulgaris Essential Oil in Treating the Most Common Bacterial Contaminants and Salmonella enterica subsp. enterica Serovar Derby in Poultry Litter

“…The choice of TEO and the concentration to be used was based on its antimicrobial effect reported in the literature [ 49 ]. Commercially available natural TEO (Specchiasol S.r.l., Bussolengo, VR, Italy) stored in a brown glass bottle at the temperature of 0–4 °C was used in the experimental design.…”

“…Commercially available natural TEO (Specchiasol S.r.l., Bussolengo, VR, Italy) stored in a brown glass bottle at the temperature of 0–4 °C was used in the experimental design. The composition of TEO was confirmed by chromatography hyphenated with mass (GC/MS) technique [ 15 , 49 ]. To achieve the proper solubilization of TEO, suitable for all the experimental procedures, the mother solution was serially diluted in 5mL Brain Heart Infusion (BHI) (Oxoid, Milan, Italy) with 10% dimethyl sulfoxide (DMSO), obtaining solutions ranging from a concentration of 5% ( v / v ) to 1.25% ( v / v ), corresponding to 450–112.5 µg/mL.…”

“…Minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) in broth dilution assay were assessed to investigate the potential antibacterial activity of TEO against Enterobacteriaceae pathogens, E. coli (ATCC 25922) and S. Derby (wild strain), and against mannitol salt-positive staphylococci, S. aureus isolates (ATCC 11622) according to CLSI [ 49 , 50 ]. These strains were part of the culture collections of the Department of Veterinary Medicine of the University of Bari “Aldo Moro”.…”