Antibacterial activity and interactions of plant essential oil combinations against Gram-positive and Gram-negative bacteria

Abstract

The aim of this study was to compare the antibacterial effects of several essential oils (EOs) alone and in combination against different Gram-positive and Gram-negative bacteria associated with food products. Parsley, lovage, basil, and thyme EOs, as well as their mixtures (1:1, v/v), were tested against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhimurium. The inhibitory effects ranged from strong (thyme EO against E. coli) to no inhibition (parsley EO against P. aeruginosa). Thyme EO exhibited strong (against E. coli), moderate (against S. typhimurium and B. cereus), or mild inhibitory effects (against P. aeruginosa and S. aureus), and basil EO showed mild (against E. coli and B. cereus) or no inhibitory effects (against S. typhimurium, P. aeruginosa, and S. aureus). Parsley and lovage EOs revealed no inhibitory effects against all tested strains. Combinations of lovage/thyme and basil/thyme EOs displayed antagonistic effects against all bacteria, parsley/thyme EOs against B. cereus, S. aureus, P. aeruginosa, and E. coli, and lovage/basil EOs against B. cereus and E. coli. Combinations of parsley/lovage and parsley/basil EOs exhibited indifferent effects against all bacteria. The combination of lovage/basil EO showed indifferent effect against S. aureus, P. aeruginosa, and S. typhimurium, and the combination parsley/thyme EO against S. typhimurium. Thyme EO has the highest percentage yield and antibacterial potential from all tested formulations; its combination with parsley, lovage, and basil EOs determines a reduction of its antibacterial activity. Hence, it is recommended to be used alone as the antibacterial agent.

Rapid bactericidal effect of cinnamon bark essential oil againstPseudomonas aeruginosa

“…The disc diffusion assay showed that the oils showing the greatest inhibitory effects were thyme, cinnamon bark and lemongrass. Of these, thyme EO was most effective, an observation reported previously by Semeniuc et al () where it was most effective when compared to three other oils. Although the MRSA strain used was resistant to gentamicin in this study, cinnamon bark, lemongrass, manuka, rosemary and thyme EOs all produced zones >18 mm.…”

Electrospun nanofibers comprising of silk fibroin/gelatin for drug delivery applications: Thyme essential oil and doxycycline monohydrate release study

“…In Gram‐negative bacteria, the cell membrane and cell wall structures have some barriers (e.g., outer membrane) which prevent antibiotic compounds from penetrating the cells; therefore Gram‐negative bacteria are more resistant to most antibiotics and chemical compounds in comparison to the Gram‐positive ones. Also, the superior efficacy of DCMH‐loaded mats in comparison with TEO‐loaded mats may be justified by the lipophilicity of the DCMH which can penetrate into the cell membrane more readily, and hence can deal with both Gram‐positive and Gram‐negative bacteria to a more significant extent …”

“…Also, the superior efficacy of DCMH-loaded mats in comparison with TEO-loaded mats may be justified by the lipophilicity of the DCMH which can penetrate into the cell membrane more readily, and hence can deal with both Gram-positive and Gram-negative bacteria to a more significant extent. 49 In this study, DCMH and TEO were separately loaded on to the scaffolds with concentrations of 94.5 and 476.3 mg, respectively. It has been reported that DCMH concentrations beyond 200 mg have not any cytotoxicity effect on fibroblast cells.…”

Characterization of essential oils extracted from different aromatic plants by FTIR spectroscopy

“…Essential oils were extracted by hydrodistillation (50 g of dried leaves with 750 mL distilled water) using a Clevenger-type apparatus (for 3 hours). The extracts were dried over anhydrous sodium sulphate and stored at 4ºC until analysis (Semeniuc et al, 2017). A Shimadzu Fourier Transform Infrared Spectrophotometer (IRPrestige-21) equipped with a Horizontal Attenuated Total Reflectance (HATR) accessories was used to collect FTIR spectra.…”