Methicillin-Resistant Staphylococcus aureus (MRSA)

Overview

What is methicillin-resistant Staphylococcus aureus (MRSA)?

Methicillin-resistant Staphylococcus aureus (MRSA) are a type of staphylococcus or "staph" bacteria that are resistant to many antibiotics. Staph bacteria, like other kinds of bacteria, normally live on your skin and in your nose, usually without causing problems. MRSA is different from other types of staph because it cannot be treated with certain antibiotics such as methicillin.

Staph bacteria only become a problem when they cause infection. For some people, especially those who are weak or ill, these infections can become serious.

MRSA infections are more difficult to treat than ordinary staph infections. This is because the strains of staph that are known as MRSA do not respond well to many types of antibiotics, which are the types of medicines normally used to kill bacteria. When methicillin and other common antibiotic medicines do not kill the bacteria that is 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 outsmart antibiotics so that these medicines no longer work well. This is why MRSA and other antibiotic-resistant bacteria are sometimes called "super bugs."

What causes an infection?

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.

MRSA used to infect people who had chronic illnesses, but now MRSA is becoming more common in healthy people. These infections can occur among people who are likely to have 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).

What are the symptoms of 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 cough.

Community-associated MRSA commonly causes skin infections, such as boils, abscesses, or 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.

How is an infection diagnosed?

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 on his or her skin but who is not sick. This is done by taking a swab from the inside of the nose.

How is an infection treated?

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. You might also be given an ointment to put on your skin or inside your nose and be asked to wash your skin daily with an antibiotic soap called chlorhexidine (Hibiclens) to reduce MRSA bacteria on your skin.

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.

If 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, it is important to call your doctor if your infection does not get better as expected.

How can I prevent getting or spreading MRSA?

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 MRSA.

You can also take steps to protect yourself from MRSA.

  • Practice good hygiene.
    • Keep your hands clean by washing them frequently and thoroughly with soap and warm water or using an alcohol-based hand sanitizer. Hand-washing is the best way to avoid spreading germs.
    • Keep cuts and scrapes clean and covered with a bandage and avoid contact with other people’s wounds or bandages.
    • Do not share personal items such as towels or razors.
  • Be smart about using antibiotics. Know that antibiotics can help treat bacterial infections but they cannot cure viral infections. Always ask your doctor if antibiotics are the best treatment. And avoid pressuring your doctor into prescribing antibiotics when they won't help you get better.
  • Always take all your antibiotic medicine as prescribed by your doctor. Using only part of the medicine may cause antibiotic-resistant bacteria to develop.
  • Do not save any antibiotics, and do not use antibiotics that were prescribed for someone else.
  • If you are in the hospital, remind doctors and nurses to wash their hands before they touch you.

If you have an infection with MRSA, you can keep from spreading the bacteria.

  • Cover your wound with clean, dry bandages and follow your doctor’s instructions on caring for your wound.
  • Keep your hands clean. You, your family, and other people with whom you are in close contact should wash their hands often with soap and warm water or use an alcohol-based hand sanitizer, especially after changing the bandage or touching the wound.
  • Do not share towels, washcloths, razors, clothing, or other items that may have had contact with your wound or a bandage. Wash your sheets, towels, and clothes with warm water and detergent and dry them in a hot dryer, if possible.
  • Keep your environment clean by wiping all frequently touched surfaces (such as countertops, doorknobs, and light switches) with a disinfectant.

References

Other Works Consulted

  • American Academy of Pediatrics (2006). Staphylococcal infections. In LK Pickering et al., eds., Red Book: 2006 Report of the Committee on Infectious Diseases, 27th ed., pp. 598–610. Elk Grove Village, IL: American Academy of Pediatrics.
  • Centers for Disease Control and Prevention (CDC) (2005). CA-MRSA information for the public. Available online: http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_public.html.

Credits

Author Maria G. Essig, MS, ELS
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Pat Truman, MATC
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care, Medical Toxicology
Last Updated March 18, 2009

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