Isolation and identification of L. monocytogenes from different food products by cultural and biochemical methods and confirmed by molecular methods (PCR). 2. Studying the effect of some chemical preservatives (acetic acid, lactic acid, sodium benzoate , sodium acetate and sodium chloride) on growth of L. monocytogenes. 3. Studying the antibacterial activity of lactic acid bacteria against isolated L. monocytgenes. 4. Detection the ability of isolated L .monocytogenes to produce some enzymes like protease, lipase, DNase, esterase, hemolysin, leciethenase, and hupparinase . 5. Determination the sensitivity of isolated L. monocytgenes to different antibiotics.