Staphylococcus aureus is a ubiquitous pathogen causing infections in humans and domestic animals. It is often associated with bovine mastitis. Among secreted virulence factors, the leukotoxins constitute a family of toxins, which induce Ca2+ influx and pore formation that allows ethidium entry. SAOUHSC_00393 is a superantigen-like protein, type I toxin, which binds to a receptor on the cell surface and stimulates intracellular signaling pathways. These toxins are excreted by microoragism and cause damage to the host by destroying cells or disrupting normal cellular metabolism. Most exotoxins can be destroyed by heating and they are susceptible to antibodies produced by the immune system, but many exotoxins are so toxic that they may be fatal to the host before the immune system has a chance to mount defenses against it.