Virulence factor that is important for the establishment of infection in the host. EsxA is required for EsxB synthesis as well as secretion (By similarity). Modulates host cell apoptotic pathways and mediates together with EsxB the release of S.aureus from the host cell. By acting on apoptosis, plays a role in the modulation of dendritic cell-mediated immunity (By similarity). Secreted via the ESAT-6 secretion system (Ess) / type VII secretion system (T7SS). Belongs to the WXG100 family. sagEsxA-like subfamily.