The aim of this study was to investigate antibacterial activity of Origanum compactum essential oils collected at three phenological stages on Escherichia coli and Bacillus subtilis. The antibacterial activity was evaluated using the agar-well diffusion assay. The MIC and MBC values were determined using the micro-dilution assay. The investigation of the antibacterial action was carried out by the evaluation of the effect of O. compactum essential oils on the antibacterial kinetic growth, the integrity of cell membrane and permeability of the cell membrane. The anti-quorum sensing activity was tested by the inhibition of the biofilm formation. The findings of this study showed that O. compactum essential oil has potent antibacterial activities against E. coli and B. subtilis. The lowest inhibition value against B. subtilis was obtained with O. compactum essential oil at the post-flowering stage (MIC = MBC = 0.0312％ (v/v)). The antibacterial mechanisms of O. compactum essential oils are related to the disturbing of the cell mem-brane integrity and the increasing of the membrane permeability, which leads to the leakage of genetic materials (DNA and RNA). Moreover, O. compactum essential oils inhibited the formation of the biofilms, a phenotype that has been known to be quorum sensing regulated.

Objective: To determin the chemical compounds of Mentha suaveolens (M. suaveolens) and Pinus halepensis (P. halepensis) essential oils (Eos) and evaluate their antioxidant and antibacterial activities. Methods: The chemical composition of P. halepensis and M. suaveolens EOs was determined by GC-MS analysis. The antioxidant activity was evaluated using DPPH, ABTS and FRAP assays. The antibacterial effect was tested against 6 bacterial strains using the well diffusion method and micro-dilution assay. Results: The major components of P. halepensis EOs were β-caryophyllene (28.04%), myrcene (23.81%) and α-pinene (12.02%). However, piperitenone oxid (56.28%), piperitenone (11.64%) and pulegone (6.16%) were the major components of M. suaveolens EOs. M. suaveolens EOs showed remarkable antioxidant activities compared with P. halepensis EOs, showing antioxidant capacity values of IC

Traditional treatment of infectious diseases is based on compounds that aim to kill or inhibit bacterial growth. The bacterial resistance against antibiotics is a serious issue for public health. Today, new therapeutic targets other than the bacterial wall were deciphered. Quorum sensing or bacterial pheromones are molecules called auto-inducer secreted by bacteria to regulate some functions such as antibiotic resistance and biofilms formation. This therapeutic target is well-studied worldwide, nevertheless the scientific data are not updated and only recent researches started to look into its potential as a target to fight against infectious diseases. A major concern with this approach is the frequently observed development of resistance to antimicrobial compounds. Therefore, this paper aims to provide a current overview of the quorum sensing system in bacteria by revealing their implication in biofilms formation and the development of antibiotic resistance, and an update on their importance as a potential target for natural substances.