الفهرس 
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Abstract
The present study aimed to isolation and identification of Staph. aureus strain from meat samples at which Staphylococcus aureus is one of the leading causes of food-borne diseases worldwide, it is a chief foodborne pathogen in raw and ready-to-eat meat products .Sixty samples of meat products signified by minced meat, sausage, beef burger, kofta and luncheon (12 of each) were randomly gathered from different supermarkets in Gharbia governorate, Egypt and test their antibiotic sensitivity using the disc diffusion method.
Antibiogram resistance profiles (ARPs) of a selected number (20) S. aureus strains against 12 test antimicrobial agents of different classes were determined. ARP data showed that 25% were resistant to at least one antimicrobial agent. However, most of the strains (70%) were multi-drug resistant MDR (i.e. these strains were resistant to three or more of the test antimicrobial agents/classes). Finally, just one strain (S14) was resistant to all test antimicrobial agents/classes and therefore classified as a pan-drug resistance strain and this sample subjected to conventional morphological, biochemical and molecular characterization.
Then explores the effectiveness of plant extracts against pan drug resistant and enterotoxigenic Staphylococcus aureus after using PCR assay for detection of enterotoxins and antimicrobial resistant genes. Four medicinal plant extracts were examined for antimicrobial activity against Staphylococcus aureus and all the four using plant extracts revealed antimicrobial activity but they differed in their relative activities. The largest zone of inhibition was observed from extracts of artemisia effects (zone of inhibition ≥35 mm) that methanolic extract of Artemisia herbal-alba show significant inhibitory activity against Staph. aureus.
The extract of plant that expressed antibacterial activity against pan-drug resistance S. aureus was subjected to GC-MS analysis to discover the chief components that have biological activities especially antibacterial activity, The GC-MS analysis showed that the methanol extract of A. herb alba was rich in many bioactive compounds that had significant therapeutic uses, showed the active components with their retention time (RT), molecular formula (MF), molecular weight (MW), and structure and peak area %. Also, shows each compound’s biological functions and its relevance to medicine. Camphor oil, found in abundance in Artemisia herbal-alba , has a potent antibacterial effect on S. aureus.
The relative expression of the genes regulating the production of enterotoxins and antibiotic resistance analyzed by using the 2−∆∆Ct method. The 2−∆∆Ct method is a convenient way to analyze the relative changes in gene expression from real-time quantitative PCR tests. By using the 2−∆∆Ct method ,the relative expression levels of mecA, mecC, sei, seg and seb genes were significantly decreased by Artemisia herbal‐alba treatment.
Artemisia herbal‐alba is powerful against Staph. aureus entero-toxigenic and antibiotic resistant genes as it significantly reduces the expression levels of genes mecA, mecC, sei, seg and seb to a range of 65 to 80%, by sub-MIC treatment. Artemisia herbal‐alba extract reduced the level of gene expression of mecA, sei, seg and seb (20%, 20%, 25% and 35%, respectively).