Staph infections are caused by bacteria called staphylococcus aureus. These bacteria usually live harmlessly on the surface of the skin, often in the nose, armpits, and on the buttocks. However, they can cause an infection if they get into the skin through a break, such as a cut or a bite. Staph infections can be passed from person to person, often through close skin contact or by sharing personal hygiene items, such as towels or toothbrushes. Less commonly, a staph infection can be spread through droplets in coughs and sneezes.