At a Glance
Why Get Tested?
To detect MRSA colonisation; to evaluate the effectiveness of treatment for a MRSA infection
When to Get Tested?
When your doctor wants to determine if you are colonised with MRSA, often on admission to a health care unit (eg hospital, renal dialysis unit); following treatment of a MRSA infection.
Swab of nose; occasionally swab of wound infection site or skin lesion
Test Preparation Needed?
The Test Sample
What is being tested?
These tests detect the presence of methicillin resistant Staphylococcus aureus (MRSA). MRSA are strains of Staphylococcus aureus, or "golden staph", bacteria that are resistant to the antibiotic methicillin and to related "beta lactam" antibiotics such as flucloxacillin and cefalexin. First appearing in the early 1960s, MRSA cases and outbreaks were a problem in confined populations such as hospitals, prisons, and nursing homes for decades. There is now known to be spread within the community with otherwise healthy people incurring infections from MRSA.
MRSA strains have caused a significant number of severe skin, lung, bone, and heart-related infections that have proven difficult to treat and, in some cases these prove fatal. Most hospitals have instituted measures to attempt to eradicate MRSA and to control the spread of MRSA from person to person. This has been a challenge as Staphylococcus aureus is a common bacterium that colonises the skin and is found in the nose of about 25-30% of the population. An Australian study of Staphylococcus aureus isolates collected from sites of infection have shown that MRSA causes over 30% of golden staph infections.In the community, MRSA is causing infections in people of all ages, including young, previously healthy people with no apparent risk factors. Investigations of outbreak cases often shows that the bacteria were spread in the community by MRSA colonized or infected people through close contact (such as sports or a day care) and through contact with contaminated objects (such as sports equipment, shared towels, razors, etc.). Early signs of MRSA skin infection have been mistaken as a reaction to a spider bite. MRSA may also cause a bacterial pneumonia that develops after a viral respiratory infection such as influenza.
Studies have also shown that community-acquired strains of MRSA are frequently genetically distinct from hospital-acquired strains of MRSA, indicating that they developed separately. Hospital-acquired MRSA has been typically resistant to more antibiotics routinely prescribed to treat skin infections and is sometimes found to be especially virulent, producing toxins and causing an invasive infection. The distinctions between hospital and community strains of MRSA are weakening, however, as people infected and/or colonized with community-acquired strains come into the hospital setting and as hospital patients and health care workers carry hospital-acquired MRSA into the community.
How is the sample collected for testing?
A nasal swab is collected by rotating a swab inside of each nostril. Occasionally, a swab of a wound infection site or of a skin lesion is collected.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.