It is a bacteria that is commonly found on the skin and in the nose, usually not causing any symptoms. However, sometimes it causes infections in skin and other sites in the body. "MRSA" is the abbreviation for "methicillin resistant staphylococcus aureus", a bacteria that has more resistance to common antibiotics that regular staph aureus. Decades ago, antibiotic resistant staph aureus began to emerge in hospitals and other health care settings. In the past 15 years, it has become common in the community in otherwise healthy people. It now causes 59% of skin infections seen in U.S. emergency rooms. MRSA causes the same types of infections that regular staph does but it cannot be treated by penicillin related or erythromycin related antibiotics. MRSA is not easier to spread than other staph infections.
Many people carry staph bacteria on their skin without any symptoms. But if infection occurs, infections of the skin are most common. It is commonly mistaken for a "spider bite" since it often looks like a pimple with surrounding redness and swelling. Fever and severe pain can be a sign of a deeper infection. Infections can occur anywhere but are often located at sites of previous cuts/scrapes, e.g. shaving areas, and the back of the neck, groin, buttocks, armpits, and the inner thigh.
A person can carry MRSA without symptoms for a long time before getting ill. This can make it extremely difficult to determine where a person may have acquired the bacteria. The place of onset of the symptoms of infection may have nothing to do with the place where the bacteria was acquired.
MRSA more often occurs in hospitalized patients and other health care facilities. It can also occur in people who have received multiple antibiotics, those who have close contact with people with MRSA infections, athletics teams who share equipment, tattoo recipients, and groups who are in crowded conditions such as daycare centers, jails/prisons, and the military. But also importantly, many people with MRSA infections have no risk factors.
The distinction between colonization by a bacteria versus infection by a bacteria is important.
Colonization = the presence of the bacteria but no signs of illness or infection. Staph bacteria are commonly found in the nostrils, belly button, underarms, groin, throat, rectum, and genitourinary tract.
Infection = clinical signs of illness or inflammation (pain, redness, warmth, swelling, pus, fever). These are due to the bacteria penetrating the outer skin layers such as through a cut, abrasion, or a razor nick. Treatment is indicated and usually includes an antibiotic.
Not treatment is needed for colonization. The precautions that help prevent skin bacteria from penetrating the protective skin layers are good hand hygiene and proper wound care.
An oral or topical antibiotic is prescribed by a health care provider. If an abscess is present, it may need to be drained. It is important to keep open or draining wounds covered with a bandage. Deeper infections or infections of parts of the body other than the skin are treated in a hospital setting.
Sometimes an individual will have several infections with MRSA over a period of time and decolonization of these patients (and possibly household members) may be attempted with nasal antibiotics and chlorhexidine (Hibiclens) baths. However, these efforts have not been shown to be consistently effective in preventing future MRSA infections.
Current guidelines do not recommend that contacts of a person with CA-MRSA infection be treated with antibiotics. Careful preventive measures, including washing hands, keeping wounds covered, washing bed sheets and towels, avoiding shared personal items, and cleaning common surfaces is recommended in these situations. In selected cases where interpersonal transmission is suspected, household contacts might be treated with an intranasal antibiotic and Hibiclens baths for decolonization.
Experts do not recommend widespread testing for MRSA because it is commonly found on health individuals but there is a small risk of becoming infected. And recolonization commonly occurs after treating individuals. Widespread treatment of a bacteria in a population also causes increased antibiotic resistance. Therefore, testing and treatment is generally done only when an individual has an infection.