Mastitis, an inflammation of the mammary gland, is one of the most costly and complex diseases of the dairy cows. The present study was designed to evaluate the occurrence of etiological pathogens in 412 pooled milk samples from subclinical and clinical mastitic dairy cows at level before taking up antibiotic therapy. Also to study the molecular characterization
of isolated bacteria. Samples of raw milk were taken from dairy cows in an around El -Behera, EI- Qalubia, EI- Sharkia, [Beni suef and El-[Menoufia Governorates of Egypt, for microbiological investigations. The predominant bacterial isolates from both clinical and subclinical mastitic milk samples were Escherichia coli (30.3 %) Staphylococcus aureus (29.9 %) followed by other streptococci. (28.6 %) meanwhile there was no growth in (11.2%) of samples. Subclinical mastitis (SCM) represented a major proportion of the burden of mastitis, 93.4 % .PCR protocol used for amplification and detection of (16-23srRNA gene (S. aureus), 16s rRNA gene (other streptococci) and tra T gene species specific (Escherichia coli)