The objective of study was to determine the rate of isolation of Staphylococcus aureus (S. aureus) in normal and mastitic bovine milk and their relationship with the milk composition also microbial, and chemical parameters changes in milk of normal apparently healthy bovine. Moreover, we study the effects of copper oxide Nano particles (Cuo- Nps) and chitosan Nano particles (Ch- Nps) on isolated antibiotic-resistant strains of S. aureus. One hundred milk samples (50 samples from apparently healthy lactating cows and buffaloes 25 for each) and (50 samples of mastitic milk 25 cows' milk and 25 buffaloes' milk from the neighboring animals in the same farms) were randomly collected from 10 privet farms (5 cows farm and 5 buffalo's farms) in Kafrelsheikh Governorate, Egypt.
Ten of 50 raw milk samples were positive for S.aureus (six raw cow^,s milk and 4 raw buffalo^,s milk samples) whereas 26 of 50 mastitic milk samples were positive for S.aureus (fifteen mastitic cow^,s milk samples and 11 mastitic buffalo^,s milk samples).
Our results revealed that direct relationship between isolation of S. aureus from normal milk samples and TBC, SCC, minerals (ash)g%, SNF g% and Total solid g% (significant increase) and inverse relationship with PH, Fat %, Lactose % and Water % (significant decrease), and no significant change with other parameters.
 Susceptibility test of isolated S. aureus to antibiotics show that highly susceptible to Amoxicillin+Clavulonic acid (77.77%) but high resistant to Oxytetracycline (94.44%).
PCR analysis of S. aureus for general gene (23S rRNA) was 100%, while multiplex PCR for AB resistance genes represented by Aminoglycosides resistance gene   Aac (6')/aph (2), Quinolones resistance gene (norA), and Chloramphenicol resistance gene (fexA) were 60%, 100% and 0% respectively.
On the other hand the zone of inhibition of Cuo- Nps and Ch- Nps against antibiotic resistant S. aureus isolated from milk was widest at 3200 µg/ml for each.  The MIC of Cuo- Nps and Ch- Nps was 800 ug/ml, 200µg/ml respectively, while the MBC of Cuo- Nps and Ch- Nps was 1600 (µg/ml) for each and MBC/MIC ratio for Cuo- Nps and Ch- Nps 2, 8 respectively. The treated cells of S. aureus with Cuo- NPs and Ch- NPs were investigated using scanning electron microscope (SEM) which showed noticeable effect on treated S. aureus cells.
 The study concluded   that S.aureus isolated from mastitic bovine milk shown resistance to numerous antibiotics and it transmitted to the surrounding bovine causing subclinical mastitis. Cuo- Nps and Ch-Nps have antibacterial activity against the isolated antibiotic resistant S. aureus.