The development of pathogenic Salmonella typhi strains resistant to several classes of antibiotics has become a worldwide main health care concern. Combinations of plant essential oils and drugs provide a promising approach to overcome drug resistance. This study investigates the potential antibacterial activity of EOs extracted from Rosmarinus officinalis, Salvia officinalis, and Thymus satureioides, individually and in combination with conventional antibiotics against S. typhi. The screening of 27 antibiotics was performed by the disc diffusion method, and the minimum inhibitory concentration of the selected antibiotics and EOs were determined by the broth microdilution method. At the same time, the interactions between EO and drugs were assessed by determining the fractional inhibitory concentration (FIC) using the diagonal measurement of n-way drug interactions method. The mechanism of antibacterial effect against S. typhi was evaluated by measuring the product of lipid peroxidation (MDA), potassium leakage from the bacteria cells, and scanning electron microscopy. Antibacterial screening indicated that nine antibiotics induced strong antibacterial activity against S. typhi with MIC values ranging from 2 to 85 µg/mL. Moreover, the EOs revealed an interesting effect against S. typhi, with MIC values ranging between 0.068 and 1.25 mg/mL. The combination of R. officinalis, T. satureioides EOs, and piperacillin/tazobactam provided a strong and reproducible synergistic effect against S. typhi. This combination seemed to amplify the antibacterial activity of EOs and antibiotics against S. typhi by increasing their potency in disrupting bacterial cell membrane integrity. These findings suggest that this combination could be a promising option for controlling the emergence of multidrug-resistant S. typhi.

The present study aimed to evaluate the changes in extra virgin olive oil (EVOO) after enrichment treatments with Thymus leptobotrys, a Moroccan endemic aromatic plant. The EVOO sample was supplemented with two materials obtained from the aerial parts of T. leptobotrys: powder (2.5 and 5) or essential oil (100 and 200ppm). The chemical composition analysis of T. leptobotrys extracts (essential oil and powder methanolic extract) allowed the determination of its phenolic profile. Quality parameters (acidity, peroxide value, and specific extinction coefficients), color, fatty acids composition, minor components (pigments and phenol), and Rancimat oxidative stability of the control and enriched oils were measured. Rosmarinic acid and thymusin were the main identified compounds in the powder; thymusin was identified for the first time in the essential oil where it was predominant. Generally, the enrichments did not downgrade the oil from its initial category (EVOO), according to quality indexes. Adding T. leptobotrys to EVOO, especially the essential oil, enriched its phenolic profile by allowing the migration of thymusin, a lipophile flavone, without affecting its quality parameters or color.