Mouse skin abscess model

Mouse skin abscess assays were performed as described before [38]. Outbred, immunocompetent hairless female mice between 4 and 6 weeks of age were used for the abscess model. Overnight cultures (grown in TSB) of the randomly selected 4 isolates each group in the three MRSA clades in MSSA clade were sub-cultured (1:100) in fresh TSB for and grown for 4 h. After centrifugation at 5000 × g for 10 min, cells were washed twice and resuspended in PBS. Mice were anesthetized with 2,2,2-tribromoethanol (Sigma-Aldrich) and subcutaneously inoculated with 50 μL PBS containing 10⁷ live S. aureus in the back skin. The abscess length (L) and width (W) dimensions were used to calculate the abscess area using the formula π × (L × W) after 24 h.