MRSA cellulitis is a severe inflammation of the lower layers of the skin and lower subcutaneous tissues, the dermis and hypodermis, caused by infection with methicillin-resistant Staphylococcus aureus (MRSA). MRSA is a staph infection that is frequently contracted in hospitals. Like other Staphylococcus aureus infections, it most commonly infects the patient through breaks in the skin, such as those caused by cuts, bites, or puncture wounds. It is treatable, but due to decades of evolution under the selective pressure created by widespread antibiotic use it has evolved immunity to many common antibiotics, such as penicillin. If left unchecked, a MRSA cellulitis infection can spread beyond the skin into deeper tissues, resulting in potentially fatal organ and tissue damage.
MRSA cellulitis arises most frequently in situations where large numbers of people live in close proximity, such as prisons, nursing homes, and military barracks. MRSA infection is a particular problem in hospitals, as many hospital residents have weakened immune systems and damage to the skin, either from injuries or from medical equipment, such as intravenous needles and catheters. This problem can be greatly mitigated through improved sanitation and MRSA screening, however. Infection risk is increased by physical conditions that affect circulation, such as diabetes, obesity, and pregnancy. Frequent contact with livestock or with communal facilities such as public locker rooms and gyms are also risk factors.
MRSA cellulitis appears as a tender, reddened area that spreads in the vicinity of the small boils that form in the area were the MRSA bacteria originally entered. The reddened area is unusually hot when touched. As the infection advances, the boils become increasingly painful, grow larger, and fill with pus. Unlike more superficial bacterial skin infections in the epidermis, which tend to produce continuous reddened areas with well-defined borders, the reddened area that appears as a result of cellulitis has a patchier and more diffuse appearance. It is possible for both to be present at the same time, however, so visual signs consistent with superficial infection do not necessarily rule out the possible existence of further infection deeper down.
Unchecked MRSA cellulitis in deep subcutaneous tissues can cause necrotizing fasciitis, popularly referred to as "flesh-eating bacteria," a condition in which toxins produced by the bacteria begin destroying soft tissue. If MRSA enters the sufferer's bloodstream or lymph system, it can spread through the body and cause conditions such as pyomyositis, infection of the skeletal muscles, and necrotizing pneumonia. In addition, the toxins produced by MRSA can result in fatal sepsis or toxic shock syndrome.