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 Methicillin-resistant Staphylococcus Aureus (MRSA)



What is Staphylococcus aureus?

Staphylococcus aureus, often referred to simply as "staph," are bacteria commonly carried on the skin or in the nose of healthy people. Occasionally, staph can cause an infection; staph bacteria are one of the most common causes of skin infections in the United States.


What infections are caused by S. aureus?

Most of these infections are minor (such as pimples and boils) and most can be treated without antibiotics (also known as antimicrobials or antibacterials). However, staph bacteria can also cause serious infections (such as surgical wound infections and pneumonia). In the past, more serious staph bacteria infections were treated with a certain type of antibiotic related to penicillin.


What is methicillin-resistant Staphylococcus aureus (MRSA)?

Over the past 50 years, treatment of these infections has become more difficult because staph bacteria have become resistant to various antibiotics, including the commonly used penicillin-related antibiotics. These resistant bacteria are called methicillin-resistant Staphylococcus aureus, or MRSA.


Where are staph and MRSA found?

Staph bacteria and MRSA can be found on the skin and in the nose of some people without causing illness.


Who gets MRSA?

Staph infections, including MRSA, occur most frequently among persons in hospitals and healthcare facilities (such as nursing homes and dialysis centers) who have weakened immune systems. These healthcare-associated staph infections include surgical wound infections, urinary tract infections, bloodstream infections, and pneumonia. Staph and MRSA can also cause illness in persons outside of hospitals and healthcare facilities. MRSA infections that are acquired by persons who have not been recently (within the past year) hospitalized or had a medical procedure (such as dialysis, surgery, catheters) are know as CA-MRSA infections. Staph or MRSA infections in the community are usually manifested as skin infections, such as pimples and boils, and occur in otherwise healthy people.


What is the difference between colonization and infection?

Colonization occurs when the staph bacteria are present on or in the body without causing illness. Approximately 25 to 30% of the population is colonized in the nose with staph bacteria at a given time. Infection occurs when the staph bacteria cause disease in the person. People also may be colonized or infected with MRSA, the staph bacteria that are resistant to many antibiotics.


How common are staph and MRSA?

Staph bacteria are one of the most common causes of skin infection in the United States, and are a common cause of pneumonia and bloodstream infections. Approximately 32% (89.4 million persons) and 0.8% (2.3 millions persons) of the U.S. population is colonized with S. aureus and MRSA respectively. There are an estimated 292,000 hospitalizations with a diagnosis of S. aureus infection annually in U.S. hospitals; of these approximately 43% are related to MRSA. In 2004, approximately 76% of skin and soft tissue infections in adults seen in emergency departments were caused by S. aureus; of these MRSA caused 59%. Invasive MRSA infections occur in approximately 94,000 persons each year and are associated with approximately 19,000 deaths. Of these infections, about 86% are healthcare-associated and 14% are community-associated.


How are staph and MRSA spread?

Staph bacteria and MRSA can spread among people having close contact with infected people. MRSA is almost always spread by direct physical contact, and not through the air. Spread may also occur through indirect contact by touching objects (i.e., towels, sheets, wound dressings, etc) contaminated by the infected skin of a person with MRSA or staph bacteria.


Are staph and MRSA infections treatable?

Yes. Most staph bacteria and MRSA are susceptible to several antibiotics. Furthermore, most staph skin infections can be treated without antibiotics by draining the sore. However, if antibiotics are prescribed, patients should complete the full course and call their doctors if the infection does not get better. Patients who are only colonized with staph bacteria or MRSA usually do not need treatment.


How can the spread of staph or MRSA infections be prevented?

  • Use of appropriate infection control practices by healthcare personnel (wearing gloves prior to and after contact with infectious body substances and adherence to hand hygiene)
  • Keep your hands clean by washing thoroughly with soap and water
  • Keep cuts and abrasions clean and covered with a proper dressing (e.g., bandage) until healed
  • Avoid contact with other people’s wounds or material contaminated from wounds.


Source: Centers for Disease Control and Prevention (CDC)


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