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The incrementing scope of pathogenic resistance to antibiotics has encouraged the search for antivirulence natural extracts. Therefore, our study designed to demonstrate the antimicrobial activity of an aqueous-garlic and thyme oil extracts against Gram-positive (Staphylococcus aureus) and Gram-negative (Salmonella spp.) bacteria by evaluating the influence of sub-inhibitory concentrations on the expression of the most critical virulence genes of the tested isolates.The antibacterial potential of both herbs was checked by the agar well diffusion method and minimum inhibitory concentration (MIC) assay. Interestingly, all isolates were inhibited by both extracts up to 50% concentration. Also, the MIC values of garlic extract (0.125-1µg/ml) against Salmonella isolates were lower than the values of thyme extract (0.5-8µg/ml). But in S. aureus isolates, the MIC values of thyme extract (0.25-2µg/ml) were the lowermost. Conventional PCR investigated that all S. aureus isolates carried the hlg (hemolysin) and icaA (intracellular adhesion) genes, but only six Salmonella isolates (three S. typhimurium and one each of S. kentucky, S. anatum, and S. lagos) had both the sopB (Salmonella outer protein B) and mgtC (membrane protein) genes. Real-time RT-PCR assays were performed to evaluate the extract's effect on the virulence genes. The thyme-oil extract has significantly repressed S. aureus virulence genes expression more than aqueous-garlic extract, which later one has effectively more than thyme-oil extract in downregulating the Salmonella virulence genes. In conclusion, garlic and thyme extracts can be used not only as a flavor, but also as potential antimicrobial agents against Gram-positive and negative bacteria.

Antimicrobial resistance poses a great threat and challenge to humanity. Therefore, the search for alternative ways to target and eliminate microbes from plant, animal, and marine microorganisms is one of the world’s concerns today.

| Listeriosis is classified as the third main cause of food-borne diseases and it is one of the significant bacterial zoonotic infections causing high fatality rates worldwide. The aim of this research was to isolate and characterize Listeria monocytogenes (L. monocytogenes) from different food items in Sharkia Province, Egypt. A total of 200 food samples were collected aseptically from local markets and subjected to the phenotypic and genotypic characterization of L. monocytogenes. Listeria species were isolated from 28 (56%), 9 (18%), 3 (6%) and 5 (10%) of the minced meat, poultry meat, tilapia fish, and raw milk samples, respectively. Overall, L. monocytogenes were isolated from 12 and 8 samples from urban and rural areas with percentages of 6 and 4%, respectively. Of interest, inlA, actA, prfA, and hlyA virulence genes were detected in all 20 L. monocytogenes isolates by multiplex PCR. In conclusion, L. monocytogenes is an organism of public health implications, and its recovery from the food samples sold at retail outlets indicates a breach of quality assurance.

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