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Antimicrobial Resistance > MRSA
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 methicillinresistant 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 methicillinresistant 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
Questions
What is
Staphylococcus
aureus?
Where are staph and
MRSA found?
What is the
difference between
colonization and
infection?
Who gets MRSA?
How common is
staph and MRSA?
Are staph and MRSA
infections treatable?
How are staph and
MRSA spread?
How can I prevent
staph or MRSA
infections?
What should I do if I
think I have a Staph
or MRSA infection?
What is CDC doing to
address MRSA in the
community?
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 closecontact 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, populationbased 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 people’s 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.





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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.
Top
References:
1. Lowry FD. Staphylococcus aureus infections. New
England Journal of Medicine. 1998;339:520-32.
2. Kluytmans J, Van Belkum A, Verbrugh H. Nasal
carriage of Staphylococcus aureus: epidemiology,
underlying mechanisms, and associated risks. Clin
Microbiol Rev. 1997;10:505-20.
3. Boyce JM. Methicillin-resistant Staphylococcus
aureus. Detection, epidemiology, and control measures.
Infect Dis Clinics of North Am. 1989;3:901-13.
4. Herwaldt LA. Control of methicillin-resistant
Staphylococcus aureus in the hospital setting. Am J
Medicine. 1999;106:11S-18S; discussion 48S-52S.
5. Asensio A, Guerrero A, Quereda C, Lizan M,
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Methicillin-resistant Staphylococcus aureus: a
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and epidemiology with implications for prevention and
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7. Saravolatz LD, Markowitz N, Arking L, Pohloh D,
Fisher E. Methicillin-resistant Staphylococcus aureus.
Epidemiologic oberservations during a communityacquired outbreak. Annals of Internal Medicine.
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8. CDC. Community-acquired methicillin-resistant
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9. Embil J, Ramotar K, Romance L, et al. Methicillinresistant Staphylococcus aureus in tertiary care
institutions on the Canadian prairies 1990-1992.
Infection Control and Hospital Epidemiology 1994;
15:646-51.
10. Rings T, Findlay R, Lang S. Ethnicity and
methicillin-resistant S. aureus in South Auckland. New
Zealand Medical Journal 1998; 111:151.
11. Maguire GP, Arthur AD, Boustead PJ, Dwyer B,
Currie BJ. Emerging epidemic of community-acquired
methicillin-resistant Staphylococcus aureus infection in
the Northern Territory. Medical Journal of Australia
1996; 1996; 164:721-3.
12. Collignon P, Gosbell I, Vickery A, Nimmo G,
Stylianopoulos T, Gottlieb T. Community-acquired
methicillin-resistant Staphylococcus aureus in Australia.
Australian Group on Antimicrobial Resistance. Lancet
1998; 352:145-6.
13. Groos A, Naimi T, Wolset D, Smith-Johnson K,
Moore K, Cheek J. Emergence of community-acquired
methicillin-resistant Staphylococcus aureus in a rural
American Indian community (Abstract 1230), 39th
Annual Interscience Conference on Antimicrobial Agents
and Chemotherapy, San Francisco, CA, 1999.
14. Methicillin-resistant Staphylococcus aureus skin or
soft tissue infections in a state prison—Mississippi,
2000. MMWR 2001 Oct. 26. 50 (42); 919-922.
15. Lindenmayer JM, Schoenfeld S, O’Grady R, Carney
JK. Methicillin-resistant Staphylococcus aureus in a high
school wrestling team and the surrounding community.
Archives of Internal Medicine 1998; 158:895-9.
16. Stacey AR, Endersby KE, Chan PC, Marples RR. An
outbreak of methicillin- resistant Staphylococcus aureus
infection in a rugby football team. British Journal of
Sports Medicine 1998; 332: 153-4.
17. Kallen AJ, Driscoll TJ, Thornton S, Olson PE, Wallace
MR. Increase in community-acquired methicillinresistant Staphylococcus aureus at a Naval Medical
Center. Infection Control and Hospital Epidemiology
2000; 21: 223-6
18. Hussain FM, Boyle-Vavra S, Bethel CD, Daum RS.
Current trends in community-acquired methicillinresistant Staphylococcus aureus at a tertiary care
pediatric facility. Pediatric Infectious Disease Journal
2000; 19: 1163-6.
19. Feder HM, Jr. Methicillin-resistant Staphylococcus
aureus infections in 2 pediatric outpatients. Archives of
Family Medicine 2000; 1163-6.
20. Goetz A, Posey K, Fleming J, et al. Methicillinresistant Staphylococcus aureus in the community: a
hospital-based study. Infection Control and Hospital
Epidemiology 1999; 20: 689-91.
21. Frank AL, Marcinak JK, Mangat PD,
Schreckenberger PC. Community-acquired and
clindamycin-susceptible methicillin-resistant
Staphylococcus aureus in children. Pediatric Infectious
Disease Journal 1999; 18:993-1000.
22. Price MF, McBride ME, Wolf JE, Jr., Prevalence of
methicillin-resistant Staphylococcus aureus in a
dermatology outpatient population. Southern Medical
Journal 1998: 91:369-71.
23. Herold BC, Immergluck LC, Maranan MC, et al.
Community-acquired methicillin-resistant
Staphylococcus aureus in children with no identified
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24. From the Centers for Disease Control and
Prevention. Four pediatric deaths from communityacquired methicillin-resistant Staphylococcus aureus—
Minnesota and North Dakota, 1997-1999. JAMA 1999;
282: 1123-5.
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