• Also Known As:
  • Staphylococcus aureus
  • Staph
  • Staph aureus
  • Methicillin-Resistant Staphylococcus aureus
Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

This article was
last modified The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.

What are staph infections?

Staphylococcus aureus, also called S. aureus or “staph,” is a bacterium that frequently lives on the human skin without causing illness (colonizes) and is present in the nose of about 25-30% of U.S. adults. S. aureus can exist in this form without causing symptoms or an infection. However, if there is a break in someone’s skin from a wound or surgery, or if a person’s immune system becomes weakened, then colonizing S. aureus can cause an infection.

Staph frequently causes localized skin infections, such as:

  • Infected hair follicles (folliculitis)
  • Boils (furuncles)
  • Impetigo

Staph can also cause abscesses and spread to:

  • Bones (osteomyelitis)
  • Lungs (pneumonia)
  • Blood (bacteremia or sepsis)
  • Heart (endocarditis)
  • Other organs

Staph can be passed from both infected and colonized people to other people through skin contact or through sharing contaminated objects, such as towels or razors.

About Staph Infections and MRSA


Healthcare-associated infections
Staph infections that are acquired while a person is in a hospital, long-term care facility, or other healthcare setting have been a challenge for many years. The confined population and the widespread use of antibiotics have led to the development of antibiotic-resistant strains of S. aureus.

Some of these strains are resistant to methicillin, a type of antibiotic (methicillin-resistant Staphylococcus aureus or MRSA). Infections caused by MRSA are frequently resistant to a wide variety of antibiotics and are associated with significantly higher rates of complications and death (morbidity and mortality), higher healthcare costs, and longer hospital stays than infections caused by methicillin-susceptible S. aureus.

Classic risk factors for MRSA infection in the hospital include surgery, prior antibiotic therapy, admission to an intensive care unit, exposure to a MRSA-colonized patient or healthcare worker, being in the hospital more than 48 hours, and having an indwelling catheter or other medical device that goes through the skin.

Community-acquired (CA) infections
MRSA infections have been associated with a growing number of outbreaks and deaths in non-medical settings where individuals are in close contact, such as: contact sports, daycare facilities, military units, and prisons. These infections are occurring in people who do not have any of the classic MRSA risk factors. A significant number of those affected have had to be hospitalized for what appears to be a simple but persistent skin infection or for pneumonia that develops after a bout of influenza.

Investigations of outbreaks have revealed that the CA-MRSA spreads from infected or colonized people to those around them through skin contact (such as sports-related cuts and abrasions), respiratory droplets (sneezing or coughing), or through exposure to contaminated objects (such as shared sports equipment, towels, toys, or playground equipment). Investigations have also revealed that the S. aureus strains involved in CA-MRSA are not the same strains as those that cause healthcare-associated MRSA; they are genetically distinct. The CA-MRSA are resistant to methicillin and related antibiotics (oxacillin, dicloxacillin, nafcillin) and erythromycin but remain susceptible to many other antibiotics.

Signs and Symptoms

Healthcare-associated MRSA
In the hospital, MRSA can cause very serious infections that spread to vital parts of the body. Depending on the location of the infection, it can cause signs and symptoms associated with:

  • Pneumonia, such as cough, fever, shortness of breath
  • Blood infection (bacteremia) and sepsis, such as fever, chills, rapid breathing, rapid heart rate
  • Infection of surgical sites, such as a red, swollen painful incision that does not heal

Community-acquired MRSA
In the community, MRSA infections most commonly affect the skin. They often appear:

  • In the beginning, as small red bumps that look like pimples or spider bites
  • As red, swollen, painful pustules with draining fluid or pus
  • In areas with cuts or abrasions of the skin
  • In areas of the skin with hair, such as the back of the neck, groin or armpit


MRSA Screening
A methicillin-resistant Staphylococcus aureus (MRSA) screen is a test that looks solely for the presence of MRSA and no other pathogens. It is primarily used to identify the presence of MRSA in a colonized person. Some hospitals have instituted screening to control the spread of MRSA. All patients may be screened on admission to the hospital or patients at high risk of being colonized may be screened (potential carriers).

Diagnosis of Staph Infections
Laboratory testing is used to identify the bacteria causing an infection and to determine its susceptibility to antibiotics.

  • The primary test for diagnosis of a staph infection is a culture of the affected area. This may involve a bacterial wound culture using fluid or pus from a wound, a sputum culture, a blood culture, a culture of joint fluid (synovial fluid), or culture of breast milk (in the case of an infected breast). Sometimes, multiple samples are collected to evaluate different body sites or to attempt to detect bacteria that may be present.
  • Susceptibility testing is performed if S. aureus are detected in a culture, to determine if the strain that is present is MRSA and to determine which antibiotics are likely to be effective in treating the infection.
  • Rapid tests for the detection of MRSA are available. These tests detect the mecA gene or the gene’s protein, which is PBP2a (penicillin-binding protein 2a). This is the gene or protein that confers methicillin resistance. Whereas cultures typically take 24-48 hours, these tests provide results in 2-5 hours, allowing for prompt treatment.

A variety of methods may be used to track different strains of MRSA. These are used in the investigation of the spread of MRSA within a community or region but are not used in the treatment of an individual person.


Healthcare-associated infections
Hospitals have had infection control measures in place for many years. Additional infection control and prevention strategies have been implemented at healthcare institutions to screen for and detect methicillin-resistant Staphylococcus aureus (MRSA) infection or colonization.

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. Some facilities administer nasal antibiotic and antimicrobial wipes to all patients admitted to the intensive care unit (ICU).

MRSA screening options:

  • A nasal culture (collected by inserting a swab inside the nose) is used to screen healthy people to determine whether someone has been colonized with MRSA and is a carrier.
  • Nasal swabs may also be collected to detect MRSA colonization based on rapid molecular tests, which do not grow the bacteria but detect their presence and antibiotic resistance by identifying the gene responsible for the methicillin resistance.

Currently, people with serious, invasive MRSA infections are usually treated with vancomycin. This is an antibiotic that must be administered intravenously (IV), often for several weeks. In most cases, vancomycin will help to eliminate the MRSA infection, but it does not prevent/eradicate colonization.

Community-acquired infections
National efforts are underway to raise awareness in the community about the existence of MRSA and to encourage preventive measures. Examples of steps you can take to lower your risk of getting a MRSA infection include:

  • Clean and cover cuts, scrapes and wounds until they are healed.
  • Avoid sharing personal items such as razors or towels.
  • Routinely clean shared equipment, such as sports equipment.
  • If you think you have an infection, see your healthcare practitioner.
  • Practice good hygiene such as frequent hand washing and/or the use of alcohol-based hand gels. For more on the proper way to wash your hands, visit this Centers for Disease Control and Prevention (CDC) web site.

Many sports teams and institutions have put procedures in place to more rapidly recognize and address MRSA infections. Healthcare providers are being urged to order cultures and susceptibility testing routinely with outpatient skin and wound infections, to monitor the affected person carefully for effectiveness of treatment, and to be alert for the possibility of CA-MRSA.

Outbreaks of CA-MRSA are investigated and traced back to their source in order to identify the cause, to determine whether other people may have unrecognized MRSA infections or colonization, and to reduce the potential for additional cases.

View Sources

Sources Used in Current Review

Herchline, T. (Apr 25, 2016). Staphylococcal Infections. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/228816-overview. Accessed November 2016.

Perloff, S. and Prado, C. (2014 August 18 Updated). MRSA Skin Infection in Athletes. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/108972-overview. Accessed November 2016.

Baorto, E. and Baorto, D. (Jun 30, 2016). Staphylococcus Aureus Infection. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/971358-overview. Accessed November 2016.

(2016 February 9 Updated). General Information About MRSA in the Community. CDC [On-line information]. Available online at http://www.cdc.gov/mrsa/community/index.html. Accessed November 2016.

(August 25, 2015). General Information About MRSA in Healthcare Settings. CDC [On-line information]. Available online at http://www.cdc.gov/mrsa/healthcare/index.html. Accessed November 2016.

Delgado, J. and Fisher, M. (September 2016 Updated). Staphylococcal Disease. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/StaphylococcalDz.html?client_ID=LTD. Accessed November 2016.

(2015 June 22 Updated). Methicillin-Resistant Staphylococcus aureus (MRSA). National Institute of Allergy and Infectious Diseases [On-line information]. Available online at https://www.niaid.nih.gov/research/mrsa-methicillin-resistant-staphylococcus-aureus. Accessed November 2016.

(July 14, 2014) Centers for Disease Control and Prevention. Antibiotic Resistance Threats in the United States, 2013. Available online at http://www.cdc.gov/drugresistance/threat-report-2013/index.html. Accessed November 2016.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Zinderman, C., et. al. (2004 May 18). Community-Acquired Methicillin-Resistant Staphylococcus aureus Among Military Recruits. Medscape Today from Emerg Infect Dis 10(5):941-944, 2004 [On-line article ]. Available online at http://www.medscape.com/viewarticle/474843.

Shiima, S. and Donahoe, L. (2004 April). Bacterial resistance: How to detect three types. MLO [On-line journal]. Available online through http://www.mlo-online.com.

(2003 September 3). Methicillin-Resistant Staphylococcus aureus Infections Among Competitive Sports Participants – Colorado, Indiana, Pennsylvania, and Los Angeles County, 2000-2003. MMWR 52(33):793-795, 2003 [On-line article]. Available online at http://www.medscape.com/viewarticle/460667.

Koonce, J. (2002). Methicillin Resistant Staphylococcus Aureus (MRSA): A Growing Challenge and Danger in Healthcare. Austin Community College Infectious Diseases Site [On-line information]. Available online at http://www2.austincc.edu/microbio/2993j/mrsa.htm.

Reuters Health Information (2004). Antibiotics and Virulence Factors Foster Emergence of Community-Acquired MRSA. Medscape Today from J Infect Dis 2004;189:1565-1573 [On-line article]. Available online at http://www.medscape.com/viewarticle/477474.

Vandenesch, F., et. al. (2003). Community-Acquired Methicillin-Resistant Staphylococcus aureus Carrying Panton-Valentine Leukocidin Genes: Worldwide Emergence. Medscape Today from Emerg Infect Dis 9(8):978-984, 2003 [On-line article]. Available online at http://www.medscape.com/viewarticle/460126.

Weber, S., et. al. (2003 November 18). Fluoroquinolones and the Risk for Methicillin-resistant Staphylococcus aureus in Hospitalized Patients. Medscape Today from Emerg Infect Dis 9(11), 2003 [On-line article ]. Available online at http://www.medscape.com/viewarticle/463682.

Schwaber, M., et. al. (2003 June 16). Clinical Implications of Varying Degrees of Vancomycin Susceptibility in Methicillin-Resistant Staphylococcus aureus Bacteremia. Medscape Today from Emerg Infect Dis 9(6), 2003 [On-line article ]. Available online at http://www.medscape.com/viewarticle/456295.

Lee, M., et. al. (2004 March 25). Management and Outcome of Children With Skin and Soft Tissue Abscesses Caused by Community-Acquired Methicillin-Resistant Staphylococcus Aureus. Medscape Today from Pediatr Infect Dis J 23(2):123-127, 2004 [On-line article ]. Available online at http://www.medscape.com/viewarticle/471838.

(2003 November 19). Methicillin-Resistant Staphylococcus aureus Infections in Correctional Facilities – Georgia, California, and Texas, 2001-2003. Medscape Today from MMWR 52(41):992-996, 2003 [On-line article ]. Available online at http://www.medscape.com/viewarticle/464224.

Salgado, C. and Farr, B. (2003 May 22). Drug Resistance, MRSA and VRE: Preventing Patient-to-Patient Spread. Medscape Today from Infect Med 20(4):194-200, 2003 [On-line article]. Available online at http://www.medscape.com/viewarticle/452426.

Chambers, H. (2001). The Changing Epidemiology of Staphylococcus aureus. Medscape Today from Emerg Infect Dis 7(2), 2001 [On-line article]. Available online at http://www.medscape.com/viewarticle/414383.

(2004 March 16). Effects of Antibiotic Nose Ointment for Hospitalized Patients with Staphylococcus aureus. Annals of Internal Medicine Volume 140 Issue 6, Page I-36 [On-line Summaries for Patients]. Available online at http://www.annals.org/cgi/content/full/140/6/I-36.

(2003 August). Community-Associated MRSA, Frequently Asked Questions. CDC, Issues in Healthcare Settings [On-line information]. Available online at http://www.cdc.gov/ncidod/hip/ARESIST/mrsa_comm_faq.htm.

(2003 March 7). MRSA – Methicillin Resistant Staphylococcus aureus, Fact Sheet. CDC, Issues in Healthcare Settings [On-line information]. Available online at http://www.cdc.gov/ncidod/hip/ARESIST/mrsafaq.htm.

(2004 April, Updated). VISA/VRSA, Vancomycin-Intermediate/Resistant Stapylococcus aureus. CDC, Issues in Healthcare Settings [On-line information]. Available online at http://www.cdc.gov/ncidod/hip/Lab/FactSheet/vrsa.htm.

Bowser, A. (2004 April 22). Community-Onset MRSA May Be Less Obvious Than in the Hospital. Medscape Today [On-line information]. Available online at http://www.medscape.com/viewarticle/474245.

Quinonez, J. (2004 January 20). Pediatric Infectious Disease Issues: Smallpox, Combination Vaccines and Methicillin-resistant Staphylococcus aureus. Medscape Today [On-line information]. Available online at http://www.medscape.com/viewarticle/466494?src=sidesearch.

(2003 October 20). Increasing MRSA in California jails. Infectious Diseases Society of America (by EurekAlert) [On-line Public release]. Available online at http://www.eurekalert.org/pub_releases/2003-10/idso-imi102003.php.

Mayo Clinic staff (2003 August 5). Toxic shock syndrome. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/invoke.cfm?id=DS00221.

(2003 August 22). Methicillin-Resistant Staphylococcus aureus Infections Among Competitive Sports Participants — Colorado, Indiana, Pennsylvania, and Los Angeles County, 2000—2003. CDC, MMWR 52(33);793-795 [On-line information]. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5233a4.htm.

(2003 October 17). Methicillin-Resistant Staphylococcus aureus Infections in Correctional Facilities — Georgia, California, and Texas, 2001—2003. CDC, MMWR 52(41);992-996 [On-line information]. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5241a4.htm.

Shopsin, B. and Kreiswirth, B. (2001). Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus. Medscape Today from Emerg Infect Dis 7(2), 2001 [On-line article]. Available online at http://www.medscape.com/viewarticle/414415.

Estrada, B. (2004 March 2). MRSA in Patients With Cystic Fibrosis. Medscape Today from Infect Med 21(1):13, 2004 [On-line article]. Available online at http://www.medscape.com/viewarticle/468210.

Capriotti, T. (2004 January 1, posted). Preventing Nosocomial Spread of MRSA is in Your Hands. Medscape Today from Dermatol Nurs 15(6):535-538, 2003[On-line article]. Available online at http://www.medscape.com/viewarticle/466141.

(2003 February 7). Public Health Dispatch: Outbreaks of Community-Associated Methicillin-Resistant Staphylococcus aureus Skin Infections — Los Angeles County, California, 2002—2003. CDC MMWR 52(05);88 [On-line article]. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5205a4.htm.

Caused By Gram-Positive Cocci, Staphylococcal Infections. The Merck Manual of Diagnosis and Therapy, Section 13. Infectious Diseases. Chapter 157. Bacterial Diseases, Topics, Caused By Gram-Positive Cocci [On-line information]. Available online at http://www.merck.com/mrkshared/mmanual/section13/chapter157/157a.jsp.

Staphylococcal Infections. The Merck Manual of Diagnosis and Therapy, Section 17. Infections, Chapter 190. Bacterial Infections, Topics: Staphylococcal Infections [On-line information]. Available online at http://www.merck.com/mrkshared/mmanual_home2/sec17/ch190/ch190r.jsp.

(2004 January 2). Update: Influenza-Associated Deaths Reported Among Children Aged <18 Years — United States 2003–04 Influenza Season. CDC MMWR 52 51 1254-1255. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5251a4.htm.

Estrada, B. (2003). Pediatric Bulletin, Will MRSA Become a Frequent Cause of Otitis? Medscape Today from Infect Med 20(3):116, 2003 [On-line article]. Available online at http://www.medscape.com/viewarticle/451588.

Forbes BA, Sahm DF, Weissfeld AS, eds., Bailey and Scott’s Diagnostic Microbiology, 12th edition, St. Louis, MO (2007), Ch. 16.

Centers for Disease Control and Prevention. Overview of Healthcare-associated MRSA. (Online information). Available online at http://www.cdc.gov/ncidod/dhqp/ar_mrsa.html. Accessed December 2007.

Centers for Disease Control and Prevention. Overview of Community-associated MRSA. (Online information). Available online at http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca.html. Accessed December 2007.

Centers for Disease Control and Prevention. Questions and Answers about Methicillin-Resistant Staphylococcus aureus (MRSA) in Schools. (Online information). Available online at http://www.cdc.gov/Features/MRSAinSchools/. Accessed December 2007.

Columbus Public Health Department, Programs and Services. MRSA awareness. (Online information). Available online at http://www.publichealth.columbus.gov/programs/Environmental_Health/mrsa.asp. Accessed December 2007.

(May 8, 2007) Herchline T. Staphylcoccal Infections. eMedicine (Online information). Available online at http://www.emedicine.com/med/topic2166.htm. Accessed December 2007.

Henry’s Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007, Pp 1017-1020.

Herchline, T. (Updated 2011 May 23). Staphylococcal Infections. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/228816-overview. Accessed June 2011.

Mayo Clinic Staff (2011 June 9) Staph infections. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/staph-infections/DS00973/METHOD=print. Accessed June 2011.

Delgado, J. and Fisher, M. (Updated 2010 October). Staphylococcal Disease. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/StaphylococcalDz.html. Accessed June 2011.

(2010 December 2). Diagnosis and Testing of MRSA Infections. CDC [On-line information]. Available online at http://www.cdc.gov/mrsa/diagnosis/index.html. Accessed June 2011.

Bush, L. et. al. (Revised 2009 December). Staphylococcal Infections. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merckmanuals.com/professional/sec14/ch171/ch171c.html. Accessed June 2011.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 1052-1053.

(January 2, 2008) U.S. Food and Drug Administration Press Release. FDA Clears First Quick Test For Drug-Resistant Staph Infections Test Identifies MRSA Bacterium in Two Hours. Available online at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm161552.htm. Accessed Sept 2011.

(May 6, 2011) U.S. Food and Drug Administration. Press Release, FDA clears first test to quickly diagnose and distinguish MRSA and MSSA. Available online at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm254512.htm. Accessed Sept 2011.

(May 18, 2011) Diekemma D. Using Viruses to Detect MRSA and MSSA in Blood Cultures. Journal Watch Infectious Diseases. Available online at http://infectious-diseases.jwatch.org/cgi/content/short/2011/518/1. Accessed Sept 2011.

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

Landro, L. New Tack in Preventing Hospital Infections: Germ-Killing Soap-Ointment Treatment for all ICU Patients Shown to Be More Effective Than Isolating Some After Screening. Wall Street Journal. Thursday, May 30, 2013, page A7. Available online at http://online.wsj.com/article/SB10001424127887324682204578513393292747314.html. Accessed July 2013.