MRSA - Methicillin Resistant Staphylococcus aureus
Fact Sheet
The Centers for Disease Control and Prevention (CDC) has received inquiries about infections with antibiotic-resistant
Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA]) among persons who have no apparent contact with the
healthcare system. This fact sheet addresses some of the most frequently asked questions.
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. 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, most serious staph bacteria infections were treated with a certain type of antibiotic
related to penicillin. 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 (1). 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. Top
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 (2).
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. Top
Who gets MRSA?
Staph bacteria can cause different kinds of illness, including skin infections, bone infections, pneumonia, severe life-threatening
bloodstream infections, and others. Since MRSA is a staph bacterium, it can cause the same kinds of infection as staph in
general; however, MRSA occurs more commonly among persons in hospitals and healthcare facilities.
MRSA infection usually
develops in hospitalized patients who are elderly or very sick or who have an open wound (such as a bedsore) or a tube going
into their body (such as a urinary catheter or intravenous [IV] catheter). MRSA infections acquired in hospitals and healthcare
settings can be severe. In addition, certain factors can put some patients at higher risk for MRSA including prolonged hospital
stay, receiving broad-spectrum antibiotics, being hospitalized in an intensive care or burn unit, spending time close to other
patients with MRSA, having recent surgery, or carrying MRSA in the nose without developing illness (3-6).
MRSA causes illness in persons outside of hospitals and healthcare facilities as well. Cases of MRSA diseases in the
community have been associated with recent antibiotic use, sharing contaminated items, having active skin diseases, and living
in crowded settings. Clusters of skin infections caused by MRSA have been described among injecting drug-users (7,8), aboriginals
in Canada (9), New Zealand (10) or Australia (11,12), Native Americans in the United States (13), incarcerated persons (14),
players of close-contact sports (15,16) and other populations (17-23). Community-associated MRSA infections are typically
skin infections, but also can cause severe illness as in the cases of four children who died from community-associated MRSA
(24). Most of the transmission in these settings appeared to be from people with active MRSA skin infections. Top
How common is 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. Staph and MRSA infections are not routinely reported to public health authorities, so a precise
number is not known. According to some estimates, as many as 100,000 persons are hospitalized each year with MRSA infections,
although only a small proportion of these persons have disease onset occurring in the community. Approximately 25 to 30% of
the population is colonized in the nose with staph bacteria at a given time (2). The numbers who are colonized with MRSA at
any one time is not known. CDC is currently collaborating with state and local health departments to improve surveillance
for MRSA. Active, population-based surveillance in selected regions of the United States is ongoing and will help characterize
the scope and risk factors for MRSA in the community. Top
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. Top
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, clothes, workout areas, sports equipment) contaminated by the infected skin of a person with
MRSA or staph bacteria. Top
How can I prevent staph or MRSA infections?
Practice good hygiene
1. Keep your hands clean by washing thoroughly with soap and water
2. Keep cuts and abrasions clean and covered with a proper dressing (e.g., bandage) until healed
3. Avoid contact with other peoples wounds or material contaminated from wounds.
What should I do if I think I have a Staph or MRSA infection?
See your healthcare provider.
What is CDC doing to address MRSA in the community?
CDC is concerned about MRSA in communities and is working with multiple partners on prevention strategies.
CDC is working with 4 states in a project to define the spectrum of disease, determine populations affected, and developing
studies to define who is at particular risk for infection
CDC is working with state health departments to assist in the
development of surveillance systems for tracking MRSA in the community
CDC is using the National Health and Nutritional
Evaluation Survey (NHANES) to estimate the number of individuals in the United States who carry staph bacteria in their nose
CDC works with laboratories across the country to improve the detection of MRSA through training personnel and use of
appropriate testing methods
CDC provides technical expertise to hospitals and state and local health departments on infection
control in healthcare settings, including control of MRSA
CDC laboratories are working to characterize the unique features
of MRSA strains from the community.
