Abstract
Background:
Staphylococcus (S.) aureus describes the greatest common cause of mastitis in sheep. however, little information was available concerning methicillin-resistant S. aureus (MRSA) in milk of mastitic sheep.

Aim:
The current study aimed to find exactly the incidence of S. aureus and MRSA in milk samples from sheep farmhouses in Mosul city, in addition to discover specific genes that encode virulence factors.

Methods:
Samples of sixty sheep's subclinical milk were gathered between October 2023 and February 2024 from various places around the Nineveh governorate. Standard methods which include selective media and biochemical testing were utilized in the current study. Furthermore, the nuc, mecA, clfA, clfB, and coa genes in the S. aureus were determined utilizing a PCR technique.

Results:
According to our findings, S. aureus was found in sheep subclinical mastitis at a rate of 23.3% (14/60) in sheep milk. Furthermore, all S. aureus isolates 100% appeared carrying of the nuc, mecA, clfA, and coa genes, while 92.9% isolates were positive for the clfB gene. The gene profiles of S. aureus isolates were divided into two primary categories. Based on of the clfA, clfB, and coa genes, nine unique strains of S. aureus sequences were submitted in the NCBI GenBank. The Phylogenetic tree analysis of all study isolates demonstrated its identity to various strains in the NCBI-BLAST.

Conclusion:
The incidence of S. aureus infections emphasized the presence of an issue in husbandry practices, insufficient adherence to basic hygiene protocols, and the random use of antibiotics.

Key words: Phylogenetic analysis tree, S. aureus, Sheep milk, Virulence factors