At a Glance

Why Get Tested?

To determine whether you are a carrier of the bacteria methicillin-resistant Staphylococcus aureus (MRSA) and could potentially spread it to other people

When To Get Tested?

When you have no signs or symptoms of an active infection, but a health care practitioner wants to determine if you are a MRSA carrier, such as when you are hospitalized

Sample Required?

Swab of the nose; occasionally, swab of wound infection site or skin lesion

Test Preparation Needed?

None

What is being tested?

Methicillin-resistant Staphylococcus aureus (MRSA) are strains of Staphylococcus aureus, or “staph,” bacteria that are resistant to the antibiotic methicillin as well as to related beta-lactam antibiotics, such as oxacillin, penicillin, amoxicillin, and cephalosporins, that are used to treat ordinary staph infections. MRSA testing detects the presence of MRSA in a patient’s sample.

Staphylococcus aureus frequently colonizes the human skin and is present in the nose of about a third of U.S. adults. It does not usually cause illness or symptoms. However, if there is a break in someone’s skin from a wound or surgery, or if someone’s immune system is weakened, then colonizing S. aureus can cause an infection.

Widespread use of antibiotics over the past several decades have led to the development of antibiotic-resistant strains of S. aureus. Infection with these strains can cause skin infections and potentially more severe, life-threatening infections such as pneumonia, bloodstream infections (septicemia), or infections at a surgical site. However, according to the Centers for Disease Control and Prevention (CDC), less than 2% of the population carries the type of staph bacteria known as MRSA.

MRSA can be spread in health care settings and in the community. Contaminated hands, medical equipment, and surfaces in places such as hospitals, clinics, or nursing homes allow the spread of MRSA from colonized or infected patients. In the community, anything that allows for skin-to-skin contact can spread MRSA. This includes sharing personal care items, participating in contact sports, or living or working in close contact with others.

Most hospitals have instituted measures to attempt to eradicate MRSA and to control the spread of MRSA from person to person. Those who test positive for MRSA may be isolated to prevent the spread to others and/or decolonized with a nasal antibiotic ointment and daily cleansing with special antimicrobial wipes. However, exactly how to implement MRSA screening and control in healthcare settings remains somewhat controversial. For example, a 2014 study comparing prevention strategies for bloodstream infections found that treating to eliminate MRSA from intensive care unit (ICU) patients who screen positive was not as effective at reducing these infections as treating all patients admitted to the ICU. This treatment may involve administering antibiotics within the nose and cleansing patients with special antimicrobial wipes. As a result, hospital policies may change in the future and less MRSA screening may be performed in these settings.

How is the sample collected for testing?

A nasal swab is collected by rotating a swab inside each nostril. Occasionally, a swab of a wound infection site or skin lesion is collected.

Common Questions

How is it used?

A methicillin-resistant Staphylococcus aureus (MRSA) screen tests solely for the presence of MRSA and no other microbes. It is primarily used to identify the presence of MRSA in a colonized person so they can be treated to eliminate MRSA and prevent its spread to others.

Often, the test is used to screen for MRSA in patients in hospitals, especially in intensive care units. On a community level, MRSA screening may be used to help determine the source of an outbreak. On a national level, additional testing may inform clinicians and researchers about the unique genetic characteristics of the strains of MRSA circulating in the community or healthcare setting.

MRSA screening tests include:

Bacterial culture – a nasal swab is collected from the nares (nostrils) of an asymptomatic person and cultured (put onto a special nutrient medium, incubated, and then examined for the growth of characteristic MRSA colonies). A swab may be collected from a wound site or skin lesion of a person who has been previously treated for a MRSA infection and cultured similarly. A screening culture identifies the absence or presence of MRSA and usually takes 1 to 2 days for a result.
Molecular tests for MRSA screening can detect nasal or wound carriage within hours, allowing for prompt treatment as necessary. The same specimen types are used in a molecular test, but the specimen is analyzed for the genetic markers to identify S. aureus and the mecA gene that confers resistance to methicillin, oxacillin, nafcillin, dicloxacillin, and other similar antibiotics. Molecular MRSA screening is becoming more widespread.

Some hospitals have instituted measures to control the spread of MRSA by screening those patients they feel are at risk of being colonized with these resistant bacteria (a carrier) or all new admissions to the hospital. When an outbreak of MRSA is under investigation, screening of healthcare workers, family members, and close contacts may be performed to identify the source of the infection and to help devise a plan to contain these infections. In some settings, such as nursing homes, a large number of people may be screened to evaluate the spread of colonization in a specific population.

When is it ordered?

A MRSA screening test may be ordered when a healthcare practitioner, hospital, or health department needs to evaluate potential MRSA colonization in an individual, their family members, and/or a group of people in the community as the source of a MRSA infection.

Specific populations that have close physical contact, such as a sports team, residents of a nursing home, or healthcare workers, may be tested for MRSA carrier status when an outbreak of MRSA is suspected.

Occasionally, a person who has been treated for MRSA may be screened to determine whether MRSA are still present.

What does the test result mean?

If either a culture or a molecular test is positive for MRSA, then the bacteria are present at the site that was tested, such as the nostrils or a wound site.

If the nasal screen or wound site culture is negative, then MRSA are either not present or are present in numbers too low to be detected by the test.

Is there anything else I should know?

Further testing may be performed on MRSA bacteria when they are isolated in a culture. These additional research tests can identify the type and subtype of S. aureus strains. Although the typing may not be used to determine treatment of the patient, it provides information to track the pattern of disease spread of the infection and characterize the toxins and other virulence factors present in the bacteria.

Can I get MRSA more than once?

Yes, being successfully treated for MRSA colonization does not prevent you from getting it again.

Can I be colonized with MRSA and not know it?

Yes, those who are carriers are healthy individuals without signs and symptoms of infection.

How can I protect myself from getting a MRSA infection?

You should wash your hands thoroughly and frequently and always clean and cover an open wound with a protective bandage.

Avoid sharing personal items, such as towels, soap, razors, or sports equipment, and wash athletic clothes after each wearing.

Related Images

Methicillin-resistant Staphylococcus aureus (MRSA) are strains of "staph" bacteria that are resistant to the antibiotic methicillin and related antibiotics. Imaged credit: Frank Deleo, CDC
A culture of MRSA. Image credit: M. Dankel, J. Gathany, CDC

View Sources

Sources Used for Current Review

MRSA. KidsHealth.org. Available online at http://kidshealth.org/parent/infections/bacterial_viral/mrsa.html. Accessed January 2017.

Coia, J. E. and Reilly, J. (2014 February). Screening for meticillin resistant Staphylococcus aureus (MRSA): who, when, and how? BMJ. Available online at http://www.bmj.com/content/348/bmj.g1697. Accessed January 2017.

(Updated 2014 March). Methicillin-resistant Staphylococcus aureus (MRSA). FamilyDoctor.org. Available online at https://familydoctor.org/condition/methicillin-resistant-staphylococcus-aureus-mrsa/. Accessed January 2017.

Mayo Clinic Staff. (2015 September 9). MRSA infection. Mayo Clinic. Available online at http://www.mayoclinic.com/health/mrsa/DS00735. Accessed January 2017.

(Updated 2016 April 15). Laboratory Testing for MRSA. Centers for Disease Control and Prevention. Available online at https://www.cdc.gov/mrsa/lab/index.html. Accessed January 2017.

(Updated 2016 May 16). Methicillin-resistant Staphylococcus Aureus (MRSA) Infections. Centers for Disease Control and Prevention. Available online at http://www.cdc.gov/mrsa/. Accessed January 2017.

Sources Used in Previous Reviews

Harbarth, S. et. al. (2006 February 27). Evaluation of Rapid Screening and Pre-Emptive Contact Isolation for Detecting and Controlling Methicillin-Resistant Staphylococcus Aureus in Critical Care, An Interventional Cohort Study. [On-line information]. Available online at http://www.medscape.com/viewarticle/523530.

(2005 February 2). Laboratory Detection of: Oxacillin/Methicillin-resistant Staphylococcus aureus. CDC [On-line information]. Available online at http://www.cdc.gov/ncidod/dhqp/ar_lab_mrsa.html.

(2005 February 3). Community-Associated MRSA Information for Clinicians. CDC [On-line information]. Available online at http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_clinicians.html.

(2006 March 7). The Growing Menace of Community-Acquired Methicillin-Resistant Staphylococcus aureus. Annals of Internal Medicine v144 (5).

Seybold, U. et. al. (2006 March 1). Emergence of Community-Associated Methicillin-Resistant Staphylococcus aureus USA300 Genotype as a Major Cause of Health Care-Associated Blood Stream Infections. CID 2006:42 pp 647-654 [On-line journal].

Fridkin, S. (2005 April 7). Methicillin-Resistant Staphyloccus aureus Disease in Three Communities. N Engl J Med 352;14.

Case, M. (2006 March 15). Fast staph test limits spread, at a high price. Post-gazette.com [On-line information]. Available online at http://www.post-gazette.com/pg/pp/06074/670567.stm.

Peck, P. (2006 February 6). Fast MRSA Test Cuts Infection Rate in Medical ICU. Medpage Today [On-line information]. Available online at http://www.medpagetoday.com/tbprint.cfm?tbid=2623.

Waknine, Y. (2006 March 31). Highlights from MMWR: Outbreaks of MRSA Infection in Newborns and More [On-line information]. Available online at http://www.medscape.com/viewarticle/528952.

Kuehnert, M. et. al. (2005). Methicillin-Resistant Staphylococcus aureus Hospitalizations, United States. Medscape from Emerg Infect Dis 11 (6) [On-line information]. Available online at http://www.medscape.com/viewarticle/505669.

Creech II, C. et. al. (2005 July). Increasing Rates of Nasal Carriage of Methicillin-Resistant Staphylococcus aureus in Health Children. The Pediatric Infectious Disease Journal v24 (7) 617-621.

Bradley, S. (2006 February 22). Staphylococcus aureus Pneumonia: Emergence of MRSA in the Community. Medscape from Semin Respir Crit Care Med [On-line information]. Available online at http://www.medscape.com/viewarticle/521338.

(2006). “Search and Destroy” Strategy Can Reduce Nosocomial MRSA Prevalence. Medscape from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/527548.

(2006). New Test Diagnoses MRSA in One Day. Medscape from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/523635.

Goossens, H. (2006). Antibiotic Resistance: Highlights of the 16th European Congress on Clinical Microbiology and Infectious Diseases. Medscape [On-line information]. Available online at http://www.medscape.com/viewarticle/530824.

Bartlett, J. (2005). Methicillin-Resistant Staphylococcus aureus and Clostridium difficile – Deal Bacterial Threats. Medscape [On-line information]. Available online at http://www.medscape.com/viewarticle/520186.

(2006). Community-Acquired MRSA a Leading Cause of Skin and Soft-Tissue Infections. Medscape from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/524998.

David, M. et. al. (2006 April 21). Contrasting Pediatric and Adult Methicillin-resistant Staphylococcus aureus Isolates. Medscape from Emerg Infect Dis 12(4): 631-637. Available online at http://www.medscape.com/viewarticle/529448.

(Updated 2009 September 28). Recognize and Prevent MRSA Infections. Centers for Disease Control and Prevention [On-line information]. Available online at http://www.cdc.gov/Features/MRSAInfections/. Accessed March 2009.

(Updated 2009 June 18). FDA Clears First Quick Test For Drug-Resistant Staph Infections, Test Identifies MRSA Bacterium in Two Hours. U.S. [On-line information]. Available online at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm161552.htm. Accessed March 2009.

Dugdale, D. et. al. (Updated 2009 May 30). MRSA. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/007261.htm. Accessed March 2009.

(2010 January 21). Genetics Used to Track Transmission of MRSA Bacteria. MedlinePlus HealthDay [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/news/fullstory_94379.html. Accessed March 2009.

(Updated 2009 July 22) MRSA and the Workplace. National Institute for Occupational Safety and Health [On-line information]. Available online at http://www.cdc.gov/niosh/topics/mrsa/. Accessed March 2009.

Martinez, J. (Updated 2009 December 16). MRSA Skin Infection in Athletes. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/108972-overview. Accessed March 2009.

Susan S. Huang, et al. Targeted versus Universal Decolonization to Prevent ICU Infection. NEJM 368;24. June 13, 2103.

MayoClinic.com. MRSA infection. Available online at http://www.mayoclinic.com/health/mrsa/DS00735. Accessed July 2013.

KidsHealth.org. MRSA. Available online at http://kidshealth.org/parent/infections/bacterial_viral/mrsa.html. Accessed July 2013.

FamilyDoctor.org. Methicillin-resistant Staphylococcus aureus (MRSA). Available online at http://familydoctor.org/familydoctor/en/diseases-conditions/methicillin-resistant-staphylococcus-aureus-mrsa.html. Accessed July 2013.

Centers for Disease Control and Prevention. Methicillin-resistant Staphylococcus Aureus (MRSA) Infections. Available online at http://www.cdc.gov/mrsa/. Accessed July 2013.

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MRSA Screening