Staphylococcal toxins that act on cell membranes include alpha toxin, beta toxin, delta toxin, and several bicomponent toxins. The bicomponent toxin Panton-Valentine leukocidin (PVL) is associated with severe necrotizing pneumonia in children.[20][21] The genes encoding the components of PVL are encoded on a bacteriophage found in community-associated methicillin-resistant S. aureus (MRSA) strains