Abstract
A total of 700 different samples belonged to dairy cattle and their environments in Kafr El-Sheikh province were collected during the period extended from December 2017 till July 2018 and subjected to the ordinary scientific methods to detect and isolate Staphylococcus aureus pathogen in a trial to estimate the prevalence of mastitis induced by this pathogen. The samples included; 300 milk samples (150 samples from clinically suspected cases and another 150 samples from apparently healthy cows) and 300 swab samples collected from cows teats, milking machines and workers hands (100 samples/each) in addition to 100 samples of animals bedding materials. The results revealed that the prevalence of S. aureus from all samples was 37.65%, with highest isolation rate from samples of teat swabs (61%). Also, it was found that the prevalence of subclinical mastitis was 54.67%, where S. aureus mastitis represented 56.09% of these cases that stand for the second highest isolation rate of the pathogen. While the lowest isolation rate was recorded for bedding material samples (5%). Moreover, the antibiotic sensitivity testing of the isolated S. aureus clarified its complete resistance (100%) to Amoxyclav (30 mcg), Penicillin-G (10 units), Amoxycillin (10 mcg) and cefotaxime (30 mcg). While the highest sensitivity (64%) was recorded for Norfloxacin (10 mcg) followed by 62% sensitivity to Gentamicin (10 mcg). At last, the isolated S. aureus was tested for its sensitivity to four commercial disinfectants usually used in dairy aspects in addition to herbal extract of Rosemary (Rosmarinus officinalis); the highest sensitivity (100%) of the isolates was recorded when TH4, Virkon S® and Rosemary extract were used at concentrations of 1 %, 2% and 2% respectively. While the isolates showed lower sensitivity to Phenol and Iodine.

Key words: Bovine mastitis, Staphylococcus aureus, antibiotic resistance, disinfectant efficiency.