Evaluation of the capacity of these strains to form abscesses in a mouse renal model revealed that neither agr nor srr systems alone were capable to restore S. aureus virulence, despite the fact that the agr system rescued the production of hemolysins (probably δ-hemolysin, since S. aureus MW2 is a weak producer of α-hemolysin22). The gene discussed is SRR; the disease is abscess.