MRSA Culture

Does this test have other names?

Methicillin-resistant Staphylococcus aureus culture

What is this test?

This test looks for bacteria called methicillin-resistant Staphylococcus aureus (MRSA) in a fluid sample from your body.

MRSA is a type of staph bacteria that is resistant to certain antibiotics. These include methicillin and related medicines like oxacillin, penicillin, and amoxicillin. MRSA infections can be life-threatening. Outbreaks can affect patients and visitors in hospitals and other health care settings. They can also happen outside of the hospital. This is commonly called community acquired.

For the test, your fluid sample will be put in a dish with special nutrients to help any bacteria grow. It can take up to 48 hours to get the results.

Rapid testing may be available. This type of testing can find MRSA within hours of culturing a sample.

Why do I need this test?

You may need this test if you have symptoms of a staph infection. Symptoms depend on the type and stage of the infection. Most MRSA infections affect the skin. A skin infection is usually red, painful, swollen, and oozing pus.

You may also have this test if you are being treated for a MRSA infection to see whether the treatment is working.

What other tests might I have along with this test?

Your doctor may also order a nucleic acid amplification test, such as the polymerase chain reaction (PCR). PCR is used to find the mecA gene. This gene can make staph bacteria resistant to certain antibiotics.

Other tests are often ordered when cultures are done to find out how far the infection has spread. They may also be done to look for other causes of symptoms. These tests include:

• Complete blood count with differential.

• C-reactive protein.

• Chemistry panel, including kidney and liver function tests.

• Echocardiogram, if your doctor thinks you have a bloodstream infection.

• Chest X-ray.

• MRI, if your doctor thinks you have a bone infection.

Discuss the results of these other tests with your doctor.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your provider what your test results mean for you.

Normal results are negative, meaning that no bacteria were found in your culture. A positive culture means you may have a MRSA infection.

How is this test done?

This test is done with a fluid sample. The sample is often taken from the infection site, such as a wound, using a sterile swab. Fluid samples can also be taken from saliva, urine, or blood. A sample may be taken from your nose to find out whether you are "colonized" with MRSA. That means you have MRSA living on your skin but aren't necessarily infected with MRSA.

For the urine test, your doctor or lab technician will give you a sterile container to collect the sample. For the blood test, a needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Other factors aren't likely to affect your results.

How do I get ready for this test?

You don't need to prepare for this test. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.