Staph infections begin when staph bacteria enters the skin or underlying soft tissue. All staph skin infections (including MRSA) start as a small red bumps that resembles a pimple, blister, or boil or an open sore or skin ulcer. When a wound becomes infected, it is often accompanied by redness, warmth and tenderness of the wound and surrounding area, discharge of pus, a yellowish-white fluid that may have a foul smell, and fever.

The infection may quickly progress to form a painful abscess (a cavity under the skin filled with pus and surrounded by inflamed tissue) which may require surgical drainage. If the bacteria remain confined to the skin, drainage may be all that is necessary to treat the infection.

MRSA infections may also penetrate through the skin into the soft tissues beneath, and when this occurs, the infection can become very dangerous. If the bacteria stays in the lower layers of skin and connective tissue, it can cause an itchy red rash that spreads called cellulitis; if it seeps into the lower connective tissues called the fascia it can cause a “flesh eating” disease known as necrotizing fasciitis. The bacteria can also penetrate and colonize soft tissues and cause life-threatening organ damage, or they can escape on to into the bloodstream and cause widespread infection. Symptoms of internal or systemic MRSA infection may include:

• Fever
• Chills
• Fatigue
• Chest pain
• Malaise
• Headache
• Muscle aches
• Rash
• Shortness of breath

Life-threatening internal MRSA infections can occur in the bones, joints, heart valves, lungs, and in the bloodstream. Infection of bone causes osteomyelitis, joint infections cause a painful arthritis, infection of the heart valves causes endocarditis, and lung infection tends to lead to pneumonia. When bacteria infect the blood it is called bacteremia and this may lead to septic shock, which is fatal in about half of cases.