الفهرس 
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Abstract
Hundred food samples representing five groups of food stuff (raw meat, frozen meat, Luncheon, karish cheese and raw milk) were randomly collected from the markets in Zagazig city, Sharqia Governorate. Microbiological analysis of the examined food samples was performed using Oxford agar medium and Baird Parker agar which are diagnostic selective media for Listeriamonocytogenesand Staphylococcispp. respectively.Fifty-seven bacterial isolates were purified and identified using morphological and biochemical characteristics; group I included 38 isolates suspected to the strains of Listeriaspp and group II included 19 isolates suspected to the strains of Staphylococcus spp.Antibiotic susceptibility profile using twelve different antibiotics revealed that four Staphylococci spp.and thirteen purified Listeria monocytogenes strains showed multiple drug resistance to 12 different antibiotics. Amplification of 16s rRNA gene in the four Staphylococci isolates confirmed their identity as Staphylococcus sciuri. The four identified strains are deposited in Genbank under accession numbers KJ000302.1, KJ000303.1, KJ000304.1 and KJ000305.1, respectively. Presence for virulence marker genes (enterotoxins genes sea, seb, sec, sed and see) and methicillin resistance gene (mec A) in the four selected strains was examined. Partial amplification of DNA of tested strains using specific primers revealed presence of seb, sec in the four tested strains and mec A gene in two strains.A lactic acid bacteria (LAB) strain isolated from pickles was preliminary identified as Lactobacillus plantarum P1 and later confirmed by detecting its 16S rRNA gene, and it was submitted to GenBank with accession number JX282192. The identified LAB strain was tested as a probiotic control against the multiple drug resistant L. monocytogenes strainUM18&S. sciuri L18 in minced meat samples alone and in combination with different concentrations of NaCl at different incubation temperatures. A reduction in L. monocytogenesUM18 &S. sciuri L18 population were nearly 4 log cycles at 0 salinity and 15°C in the presence of 107Lactobacillus plantarum P1 and the antimicrobial activity of it decreased by increasing in sodium chloride concentration