Staphylococcus aureus (S. aureus) bacteria normally are present on skin or in noses of about one-third of the population. Local skin infections caused by S. aureus are common and usually minor. When S. aureus that causes an infection can’t be killed by the antibiotic methicillin or other related beta-lactam antibiotics, it’s called MRSA. About 1% of the population carries MRSA bacteria. MRSA infections occur in hospitals or other health care settings, such as nursing homes and dialysis centers (Hospital Acquired, HA-MRSA). They also occur in the community (Community Acquired, CA-MRSA). HA-MRSA infections are usually related to procedures such as surgery or devices such as intravenous tubes. CA-MRSA infections often begin as painful skin boils. MRSA can invade deeply into the body and cause serious illness and even death.
S. aureus bacteria developed methicillin resistance after many years of this antibiotic being used to treat infections. Risks for hospital-acquired-MRSA include stays in hospitals or long-term care facilities such as nursing homes. Having medical devices such as indwelling catheters also increases the risk. Community-acquired-MRSA spreads by skin-to-skin contact and contact with mucus or droplets from coughing. Puncture wounds are another route for MRSA to enter the body. Touching contaminated towels, clothing, or other objects can spread MRSA. People playing contact sports can have skin injuries allowing MRSA infections to spread and develop. Children and others in daycare centers and people living in crowded conditions have greater risks of infection.
Skin symptoms include small red bumps that look like pimples or boils. These can become painful abscesses. MRSA may also cause styes, carbuncles, and rashes. MRSA can get deeper into the body and infect almost any organ. Life-threatening infections of bones, joints, bloodstream, heart valves, and lungs can occur. These symptoms include fever, low blood pressure, headaches, shortness of breath, joint pains, and rashes all over the body.
Diagnosis is made by getting samples of skin, pus, blood, urine, or secretions from the nose. These are cultured (grown) in a laboratory to see whether MRSA bacteria are present. A new test (PCR based) can detect MRSA in blood faster than bacterial cultures.
Some infections may not need antibiotics. Abscesses are first treated with incision and drainage. People with HA-MRSA infections can be isolated. Visitors and health care workers should wear protective clothes, and wash hands after patient contact. Room surfaces and laundry should be disinfected. Antibiotic treatment depends on which drug kills the bacteria. Possible drugs include trimethoprim/sulfamethoxazole and newer ones such as linezolid, daptomycin, quinupristin/dalfopristin, tigecycline, and telavancin.
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Copyright © 2016 by Saunders, an imprint of Elsevier, Inc.
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