Methicillin-resistant Staphylococcus aureus (MRSA)
is a type of staphylococcus or "staph" bacterium that is resistant to many
antibiotics. Staph bacteria, like other kinds of
bacteria, normally live on your skin and in your nose, usually without causing
problems. But if these bacteria become resistant to antibiotics, they can cause serious infections, especially in people who are ill or weak. MRSA is different from other types of staph because it cannot be
treated with certain antibiotics such as methicillin.
MRSA infections are more difficult to treat than ordinary
staph infections. This is because the strains of staph known as MRSA
do not respond well to many common antibiotics used to kill bacteria. When methicillin and other antibiotics do not kill the bacteria causing an infection, it
becomes harder to get rid of the infection.
MRSA bacteria are
more likely to develop when antibiotics are used too often or are not used
correctly. Given enough time, bacteria can change so that these
antibiotics no longer work well.
MRSA, like all staph bacteria, can be
spread from one person to another through casual contact or through
contaminated objects. It is commonly spread from the hands of someone who has
MRSA. This could be anyone in a health care setting or in the community. MRSA
is usually not spread through the air like the common cold or flu virus, unless
a person has MRSA
pneumonia and is coughing.
MRSA that is
acquired in a hospital or health care setting is called healthcare-associated
methicillin-resistant Staphylococcus aureus (HA-MRSA).
In most cases, a person who is already sick or who has a weakened
immune system becomes infected with HA-MRSA. These
infections can occur in wounds or skin, burns, and IV or other sites where
tubes enter the body, as well as in the eyes, bones, heart, or blood.
In the past, MRSA infected people who had chronic illnesses. But now MRSA has become more common in healthy people. These infections can occur among people
who have scratches, cuts, or wounds and who have close contact with one
another, such as members of sports teams. This type of MRSA is called
community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA).
Symptoms of a MRSA infection depend on where the
infection is. If MRSA is causing an infection in a wound, that area of your
skin may be red or tender. If you have pneumonia, you may develop a
Community-associated MRSA commonly causes skin infections,
cellulitis. Often, people think they have been bitten
by a spider or insect. Because MRSA infections can become serious in a short
amount of time, it is important to see your doctor right away if you notice a
boil or other skin problem.
If your doctor thinks that you are infected with
MRSA, he or she will send a sample of your infected wound, blood, or urine to a
lab. The lab will grow the bacteria and then test to see which kinds of
antibiotics kill the bacteria. This test may take several days.
You may also be tested if your doctor suspects that you are a MRSA
carrier. A MRSA carrier is a person who has the bacteria living on the skin and in the nose but
who is not sick. The test is done by taking a swab from the inside of the
Depending on how serious your infection is, the doctor may drain your
wound, prescribe antibiotic medicine, give you an IV (intravenous)
antibiotic, or hospitalize you.
If you have a MRSA infection and need to be in a
hospital, you may be isolated in a private room to reduce the chances of
spreading the bacteria to others. When your doctors and nurses are caring for
you, they may use extra precautions such as wearing gloves and gowns. If you
have a MRSA pneumonia, they may also wear masks.
Most cases of
community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) begin as mild skin infections such as pimples or boils.
Your doctor may be able to treat these infections without antibiotics by using
a minor surgical procedure that opens and drains the sores.
your doctor prescribes antibiotic medicine, be sure to take all the medicine
even if you begin to feel better right away. If you do not take all the
medicine, you may not kill all the bacteria. No matter what your treatment, be sure to call your doctor if your infection does not get better as
As more antibiotic-resistant bacteria develop,
hospitals are taking extra care to practice infection control, which includes
frequent hand-washing and isolation of patients who are infected with
You can also take steps to protect yourself from
If you have an infection with MRSA, you can keep from
spreading the bacteria.
If you need to go to the hospital for some reason, and you have staph bacteria living on your skin and in your nose, you may be treated to try to prevent getting or spreading a MRSA infection. You may be given an ointment to put on
your skin or inside your nose. And you need to wash your skin daily with a
special soap that can get rid of the bacteria.
Other Works Consulted
American Academy of Pediatrics (2012). Staphylococcal infections. In LK Pickering et al., eds., Red Book: 2012 Report of the Committee on Infectious Diseases, 29th ed., pp. 653–668. Elk Grove Village, IL: American Academy of Pediatrics.
Centers for Disease Control and Prevention (CDC) (2010). MRSA infections. Available online: http://www.cdc.gov/mrsa/index.html.
Kallen AJ, et al. (2010). Health care-associated invasive MRSA infections, 2005–2008. JAMA, 304(6): 641–647.
Liu C, et al. (2011). Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clinical Infectious Diseases, 52(3): 285–292.
March 10, 2013
E. Gregory Thompson, MD - Internal Medicine
& Theresa O'Young, PharmD - Clinical Pharmacy
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