Staph infections refer to any infection caused by the bacteria that belongs to the genus Staphylococcus, also called staph bacteria. While there are more than thirty species of staph, one called Staphylococcus aureus is responsible for most of the infections that cause harm in humans. Many healthy people have S. aureus on the surface of their skin, inside their nose, or in their throat. Staph infections can occur when these bacteria penetrate into deeper layers of the body.

Staph infections can take several forms ranging from simple skin boils to pneumonia, food poisoning, toxic shock syndrome, or blood poisoning. The most common type of infection, called cellulitis, affects the skin’s deeper layers. It might begin as a small area of inflammation causing tenderness, swelling, or redness on the skin’s surface, or as an open sore or skin ulcer. This type of infection is usually treatable with antibiotics. However, in recent years antibiotic resistant strains of S. aureus have become more common.