MRSA Infection (cont.)

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How is a MRSA infection transmitted or spread?

MRSA infections are contagious from person to person; occasionally direct contact with a MRSA-infected person is not necessary because the bacteria can also be spread by people who touch materials or surfaces contaminated with MRSA organisms. There are two major ways people become infected with MRSA. The first is physical contact with someone who is either infected or is a carrier (people who are not infected but are colonized with the bacteria on their body) of MRSA. The second way is for people to physically contact MRSA on any objects such as door handles, floors, sinks, or towels that have been touched by a MRSA-infected person or carrier. Normal skin tissue in people usually does not allow MRSA infection to develop; however, if there are cuts, abrasions, or other skin flaws such as psoriasis (a chronic inflammatory skin disease with dry patches, redness, and scaly skin), MRSA may proliferate. Many otherwise healthy individuals, especially children and young adults, do not notice small skin imperfections or scrapes and may be lax in taking precautions about skin contacts. This is the likely reason MRSA outbreaks occur in diverse types of people such as school team players (like football players or wrestlers), dormitory residents, and armed-services personnel in constant close contact. A recent example of this spread of MRSA occurred in three NFL football players, all members of the same team, Tampa Bay. Three players got skin infections, and one had to undergo foot surgery to rid the player of recurrent MRSA infection.

How is a MRSA infection diagnosed?

Most doctors start with a complete history and physical exam of the patient to identify any skin changes that may be due to MRSA, especially if the patient or caretaker mentions a close association with a person who has been diagnosed with MRSA. A skin sample, sample of pus from a wound, or blood, urine, or biopsy material (tissue sample) is sent to a microbiology lab and cultured for S. aureus. If S. aureus is isolated (grown on a Petri plate), the bacteria are then exposed to different antibiotics, including methicillin. S. aureus bacteria that grow well when methicillin is in the culture are termed MRSA, and the patient is diagnosed as MRSA infected. The same procedure is done to determine if someone is a MRSA carrier (screening for a carrier), but sample skin or mucous membrane sites are only swabbed, not biopsied. These tests help distinguish MRSA infections from other skin changes that often appear initially similar to MRSA, such as spider bites and skin changes that occur with Lyme disease. These tests are very important; misidentification of a MRSA infection may cause the patient to be treated with other agents like dapsone (used for spider bites). This can result in progression of the MRSA infection and even other complications due to the dapsone.

In 2008, the U.S. Food and Drug Administration (FDA) approved a rapid blood test (StaphSR assay) that can detect the presence of MRSA genetic material in a blood sample in as little as two hours. The test is also able to determine whether the genetic material is from MRSA or from less dangerous forms of staph bacteria. The test (PCR based) is not recommended for use in monitoring treatment of MRSA infections and should not be used as the only basis for the diagnosis of a MRSA infection. In addition, there are new screening tests that report detecting or ruling out MRSA infections in about five hours.

Medically Reviewed by a Doctor on 12/11/2013

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