This investigation was performed in Teaching Hospital and arm of Benha University in Moshtohor. The number of cows in this farm 80 dairy cows. 40 of them had clinical signs of mastitis (inflammation in teats, pain in milking and milk decrease in amount and quality). Weexamine these cows to identify the cause of these signs. California Mastitis Test (CMT) was performed to determine positive milk samples in the mastitic targeted cows. 20 samples of early lactation stage cows were recovered from 40 CMT- positive milk samples. Biochemical and PCR tests were performed to isolates E. Coli from positive milk samples (CMT) and determined three virulance genes, eae gene,SXT1 and SXT2. The significance of Escherichia coli-induced mastitis and biochemical changes associated to it in cows, due to the presence of virulence genes and resistance to awide range of 20 antimicrobials, is concluded. E.coli cause biochemical changes in mastitic cow as liver enzymes AST, GPT, TP,. Oxidativeenzymes as CAT, SOD, GST, LDand kidney function as urea and creatinine. E.coli has effect on inflammatory response inmastitic cow immunity system of by L6, TNF and CRP.