How Many Tests Are Required to Determine if a Person is Free of MRSA?

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An Introduction To Staphylococcus Aureus

Staphylococcus aureus (SA) is a common bacteria found in at least 1 in 3 people. It inhabits areas such as the skin, nose, or even the vagina. Even though it inhabits these areas, its ability to develop infection is relatively low. If the person’s immune system is suppressed, and if the bacteria migrates to an area of the body it does not normally inhabit, it might cause an infection. This bacteria is one of the main reasons that hospitals will carry out stringent disinfections, as a wound or cut on an ill patient can cause a staphylococcus infection at that site.

Methicillin & MRSA

Methicillin is a type of penicillin antibiotic used to treat infections with Staph aureus. It is a strong antibiotic that can kill most of the bacteria that will be resistant to any other form of penicillin. However, the use of methicillin has been discontinued due to more effective medication being created. However, the healthcare industry still refers to an epidemic of staph aureus as methicillin-resistant Staphylococcus aureus to distinguish bacteria that is resistant to being killed by any penicillin antibiotics. Even though these strains of staph aureus have undergone genetic mutations and are resistant to methicillin, there are still other antibiotics that can treat the infection.

MRSA is passed from person to person by the bacteria being on the hands or clothing. Once the person becomes sick, it is necessary to keep them in isolation or only have them around other patients who have become infected. The main signs and symptoms initially involve the skin, but the bacteria can spread to cause systemic disease. When this happens the patient’s treatment is done in a more aggressive manner. Diagnosis is done by obtaining a skin sample, and growing a colony within the laboratory. There is also a less common blood test available that detects the presence of the bacteria in the blood.

Signs & Symptoms

The most common signs and symptoms are boils, impetigo, carbuncles, cellulitis, and abscesses. In systemic disease the body can exhibit pain in the joints, fever, problems breathing, and a rash. In very severe cases the person can have infection of the heart muscle (endocarditis), infection of the bone (osteomyelitis), or the “flesh-eating disease” (necrotizing fascitis).

How many tests are required to determine if a person is free of MRSA?

Treatment is quite intensive and is one of the reasons why someone might ask, “How many tests are required to determine if a person is free of MRSA?” To treat, the physician will use other antibiotics such as vancomycin or doxycyline. In some localized infections, the physician might decide to break the boil and drain it. In more severe infections, dialysis, replenishing fluids, and oxygen might be needed. MRSA infections have a 20% mortality rate.

In regards to someone being considered free of MRSA, they will need to obtain at least three body swab tests with negative results before they can be considered free of methicillin-resistant staph aureus.


Print Source: Davidson, Stanley & C. Haslett. 2002. “Davidson’s Principles and Practice of Medicine.” Churchill Livingstone, Edinburgh.

Print Source: Cotran R, Kumar V, and Robbins, SL. 1999. Robbins Pathologic Basis of Disease, 6th Ed. W.B. Saunders Company, Philadelphia.

Web Source: WebMD, LLC., eMedicine Health. “MRSA Infection.” 2010. Available: