In this study a total of 1200 quarter milk samples were selected from 300 cows at different localities of
El-Kaliobia Governorate were examined bacteriologically and revealed that 57 S.aureus isolated from
both clinical and subclinical mastitis with incidence of 45.6% of total isolates. Molecular typing of S.
aureus by PCR revealed that all isolates (100%) (12 random S.aureus isolates) were positive for the 16
SrRNA genes of S. aureus. Genotyping of virulence genes encoding factors of S. aureus revealed that
two isolates were positive for (tst-1) gene (16.7%), three isolates positive for (etb) 25%, nine isolates
positive for each of (icaD and femA) genes (75%), seven isolates positive for (hlg) (58.3%), eight isolates
positive for (nuc) (66.7%).