Virulence factor that is important for the establishment of infection in the host. EsxA is required for EsxB synthesis as well as secretion (PubMed:15657139). 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). Mutant shows a significant reduction in the ability to establish kidney or liver abscesses in infected mice. Belongs to the WXG100 family. sagEsxA-like subfamily.