What Is MRSA?

MRSA bacteria, false color
MRSA bacteria. PASIEKA/Science Photo Library/Getty Images

Question: What is MRSA?

Answer: MRSA is the acronym for methicillin-resistant Staphylococcus aureus.

In other words, it is a type of bacteria known as Staphylococcus aureus(staph) that has become resistant to treatment with a certain class of antibiotics - methicillin. In fact, most MRSA is resistant to more than just that one type of medication. These bacteria are often actually multi-drug resistant -- meaning that infections with MRSA can only be treated with a few expensive drugs.

Fun Fact: Staphylococcus aureus is named for the yellow colored colonies the bacteria make when grown in culture. Aureus is a latin word meaning "golden."

MRSA has been around for decades, and is primarily a problem in healthcare settings. According to the CDC, more than 85% of MRSA infections take place in healthcare facilities. The people at greatest risk of acquiring MRSA are therefore those who have recently been hospitalized and people with impaired immune systems such as the elderly, people on hemodialysis with indwelling lines (permanent catheter for access to a vein), and individuals with HIV.

It is important to know that most staph infections are not MRSA infections. Although MRSA infections are relatively rare, staph infections are actually one of the most common forms of skin infection in the United States. Most staph infection are minor skin infections -- simply pimples or boils -- and don't need antibiotics for treatment.

However, staph can also cause more serious infections, such as pneumonia, infections of the heart lining (endocarditis), and blood infections, which require antibiotics for treatment. It is those types of infection in which the presence of MRSA causes the most serious problems.

Most healthy people will never need to worry about a MRSA infection, but MRSA has been a significant problem in hospitals and other healthcare facilities.

Fortunately, new procedures have been having a positive effect on the risk of people contracting nosocomial MRSA infections in the hospital. According to the CDC, the number of hospital based MRSA infections declined 54% between 2005 and 2011, and 9000 fewer individuals died of MRSA in the later year than the earlier one.

Other forms of problematic staph infections include those caused by drug resistant staph such as vancomycin-resistant staph (VRSA). Fortunately, as of the fall of 2010 all vancomycin resistant strains remained susceptible to existing antibiotics. The same can, sadly, not be said for all multi-drug resistant bacterial infections, which have the potential to be a significant public health problem, whether they are caused by staph infections or other types of bacteria.


Binh An Diep et al. "Emergence of Multidrug-Resistant, Community-Associated, Methicillin-Resistant Staphylococcus aureus Clone USA300 in Men Who Have Sex with Men" Annals of Internal Medicine 148(4) Epub Ahead of Print. (Accessed 1/22/08).

CDC Community Associated MRSA Information Page. Accessed 1/22/08 from http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_public.html.

CDC Healthcare Associated Infections Page. Accessed 7/16/15 from http://www.cdc.gov/HAI/organisms/visa_vrsa/visa_vrsa.html

CDC Methicillin-resistant Staphylococcus aureus (MRSA) Infections Page. Accessed 7/16/15 from http://www.cdc.gov/mrsa/healthcare/

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