الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
During the last decade, a great attention was paid towards probiotics as a natural feed additive, which beneficially affects the gastrointestinal flora reflecting such effect on the host general health condition. The extensive use of antibiotics in animal farms with the purpose of promoting growth rate and increasing feed conversion efficiency and for the prevention of intestinal infections have led to an imbalance of the beneficial intestinal flora and the appearance of resistant bacteria.
Salmonella enterica serovar Typhimurium is one of three serotypes, sometimes responsible for 50% of the Salmonellosis cases in humans. The susceptibility of humans and animals to Salmonella infection is generally determined by both Salmonella virulence and host factors, such as age and genetics. The infection normally starts from the intestinal phase, through which Salmonella can enter the blood circulation and spread to various organs such as the liver and spleen, leading to systemic infection. Salmonella pathogenicity island 1 (SPI-1) is critical in causing the intestinal phase of infection therefore we have investigated the probiotic properties if they are able to reduce Salmonella infection in broilers and modulate Salmonella SPI-1 virulence gene expression in our experiment or not.