ABSTRACT
 
S. aureus is one of the most important causes of nosocomial infections, main contagious pathogens that can play a vital and important role in bovine mastitis in veterinary medicine causing high worldwide economic losses, where the primary reservoir harboring the pathogens is cow, and recently recorded as zoonotic microbe which able to transmitted from human to animal and vice versa, identification of staphylococcus species mainly S. aureus become more quickly and accurate with molecular technique as phenotypic technique due to multidrug resistance developed some mutation and production of biofilm which interference phenotypic identification, as nuc gene, and coa gene become the golden standard technique for identification S. aureus and the study concerned the differentiation between phenotypic and genotypic characterization of isolates collected from milk samples of bovine mastitis,  as directed 157 phenotypic staphylococcus isolates on MSA media to biochemical phenotypic tests as 81/157 (51.6%) isolates of them were phenotypic S. aureus, and by molecular technique,  16S universal primer detected 141/157 (89.8%) were confirmed staphylococcus about 130/141(92.2%) were CoPS by coa gene detection, and 111/141 (78.7%)  were typical S. aureus detected by nuc gene, as most of them produced biofilm that detected by ica gene in 81/141(57.4%) was the main cause of interrupting the phenotypic characterization by biochemical tests.