A bacterial infection that can involve any part of the body, but most commonly affects the skin and soft tissue (cellulitis) or causes a collection of pus (abscess). Staph bacteria are commonly found on the skin and in the nose but does not always cause an infection. These people are colonized but do not actually become ill. The infection can be localized to the skin or become widespread and lethal. The infection more commonly occurs in those with weakened immune systems, burns, surgical wounds, and patients with invasive devices such as urinary catheters, intravenous catheters, dialysis catheters, or breathing tubes. Methicillin resistant staphylococcus aureus (MRSA) is a special type of staphylococcus that is becoming more common and is harder to treat, requiring special antibiotics.