This research was conducted to isolation and diagnosis of Salmonella typhimurium that caused child diarrhea infections, whom attend in Salah-Adin Teaching Hospital in Tikrit. and determine the susceptibility of isolates against some antibiotics, also, determine the Lactobacillus casei as probiotics which, isolation and identification from fermented dairy samples collected from different local in Salah-Adin governorate markets, then assay the effect of orally dosage of probiotics on some physiological and biological parameters in rats that infected with Salmonella typhimurium isolate. Salmonella typhimurium were appeared at 15 isolates from child diarrhea infections samples and the Lb. casei isolates from fermented dairy products, then identified according to morphological, microscopic, cultural and biochemical characterizes, then selective the probiotics isolate from Lb. casei which depended according to their ability to grow in pH 2 and able to tolerance growth at 0.3% bile salts, furthermore their ability to adhesion with intestine mucus surface at 43.8%.