Staphylococcus aureus proteins differentially produced in ewe gangrenous mastitis or ewe milk

Despite being one of the main pathogens involved in ruminant mastitis, little is known about what proteins Staphylococcus aureus does express, in vivo, during the infection. Here, two S. aureus strains were isolated from curds formed within the udder of two ewes suffering from gangrenous mastitis. Protein samples were prepared from cell fractions and were analyzed using 1D-LC MS/MS. Results were compared to 1D-LC MS/MS analysis of the same S. aureus strains grown in ewe milk. A total of 365 proteins were identified. Most of them were related to cellular metabolism, cellular division and stress response. Half of the proteins were found in both conditions but a substantial number were specifically found in in vivo conditions and gave indications about the active metabolic status and the stresses encountered by S. aureus within the cistern during a gangrenous mastitis.