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.
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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 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.
- 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.
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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, Martinez-Ferrer
M. Colonization and infection with methicillin-resistant Staphylococcus
aureus: associated factors and eradication. Infec Control
Hosp Epidemiol. 1996;17:20-8.
6. Mulligan ME, Murray-Leisure KA, Ribner BD, et al. Methicillin-resistant
Staphylococcus aureus: a consensus review of the microbiology,
pathogenesis, and epidemiology with implications for prevention
and management. Am J Medicine. 1993;94:313-28.
7. Saravolatz LD, Markowitz N, Arking L, Pohloh D, Fisher E. Methicillin-resistant
Staphylococcus aureus. Epidemiologic oberservations during
a community-acquired outbreak. Annals of Internal Medicine. 1982;96:11-16.
8. CDC. Community-acquired methicillin-resistant Staphylococcus
aureus infections—Michigan. MMWR. 1981;30:185-7.
9. Embil J, Ramotar K, Romance L, et al. Methicillin-resistant
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 methicillin-resistant 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 methicillin-resistant 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. Methicillin-resistant
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 predisposing risk. JAMA 1998; 279:593-8.
24. From the Centers for Disease Control and Prevention. Four
pediatric deaths from community-acquired methicillin-resistant
Staphylococcus aureus—Minnesota and North Dakota,
1997-1999. JAMA 1999; 282: 1123-5.
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