Methicillin-resistant Staphylococcus aureus (MRSA)

MRSA Bacteria
Immune system cell called a neutrophil (purple) ingesting MRSA bacteria (yellow).

Image Credit: NIAID

Methicillin-resistant Staphylococcus aureus (MRSA)

MRSA is short for methicillin-resistant Staphylococcus aureus. MRSA is a strain of Staphylococcus aureus bacteria or Staph bacteria, that have developed a resistance to penicillin and penicillin-related antibiotics, including methicillin. These drug-resistant germs, also known as superbugs, can cause serious infections and are more difficult to treat as they have gained resistance to commonly used antibiotics.

Staphylococcus aureus

Staphylococcus aureus is a common type of bacterium that infects about 30 percent of all people. In some people, it is a part of the normal group of bacteria that inhabit the body and may be found in areas such as the skin and the nasal cavities. While some staph strains are harmless, others pose serious health problems. S. aureus infections can be mild causing skin infections such as boils, abscesses, and cellulitis. More serious infections can also develop from S. aureus if it enters the blood. Traveling through the bloodstream, S. aureus can cause blood infections, pneumonia if it infects the lungs, and can spread to other areas of the body including the lymph nodes and bones. S. aureus infections have also been linked to the development of heart disease, meningitis, and serious food-borne illness.


Staphylococcus aureus (MRSA)
Staphylococcus aureus (MRSA). iLexx / iStock / Getty Images Plus

MRSA Transmission

S. aureus is typically spread through contact, primarily hand contact. Just coming in contact with the skin however, is not enough to cause an infection. The bacteria must breach the skin, through a cut for example, to get to and infect the tissue underneath. MRSA is most commonly acquired as a result of hospital stays. Individuals with a weakened immune system, those that have undergone surgery, or have implanted medical devices are more susceptible to hospital-acquired MRSA (HA-MRSA) infection. S. aureus are able to adhere to surfaces due to the presence of cell adhesion molecules located just outside of the bacterial cell wall. They can adhere to various types of instruments, including medical equipment. If these bacteria gain access to internal body systems and cause infection, the consequences could be fatal.

MRSA may also be acquired through what is known as community associated (CA-MRSA) contact. These types of infections spread through close contact with individuals in crowded settings where skin-to-skin contact is common. CA-MRSA is spread through the sharing of personal items including towels, razors, and sporting or exercise equipment. This type of contact may occur in places such as shelters, prisons, and military and sports training facilities. CA-MRSA strains are genetically different from HA-MRSA strains and are thought to spread more easily from person to person than HA-MRSA strains.

Treatment and Control

MRSA bacteria are susceptible to some types of antibiotics and are often treated with the antibiotics vancomycin or teicoplanin. Some S. aureus are now starting to develop resistance to vancomycin. Although vancomycin-resistant Staphylococcus aureus (VRSA) strains are very rare, the development of new resistant bacteria further emphasizes the need for individuals to have less access to prescription antibiotics. As bacteria become exposed to antibiotics, over time they may acquire gene mutations that enable them to gain resistance to these antibiotics. The less antibiotic exposure, the less likely the bacteria will be able to gain this resistance. It is always better however, to prevent an infection than to treat one. The most effective weapon against the spread of MRSA is to practice good hygiene. This includes washing your hands thoroughly, showering soon after exercising, covering cuts and scrapes with bandages, not sharing personal items, and washing clothes, towels, and sheets.

MRSA Facts

MRSA Facts. designer491 / iStock / Getty Images Plus
  • Staphyloccoccus aureus was discovered in the 1880s.
  • Staphyloccoccus aureus gained resistance to methicillin in the 1960s.
  • MRSA is resistant to penicillin-like antibiotics such as penicillin, amoxicillin, oxacillin and methicillin.
  • About 30 percent of all people have Staphyloccoccus aureus bacteria present in or on their bodies.
  • Staphyloccoccus aureus bacteria don't always cause infection.
  • According to the CDC, 1 percent of those with Staphyloccoccus aureus bacteria have MRSA.
  • MRSA is most commonly acquired as a result of hospital stays.

Key Takeaways

  • MRSA or methicillin-resistant Staphylococcus aureus is an insidious strain of bacteria that can cause serious infection.
  • MRSA is so deadly due to its antibiotic resistance to commonly used antibiotics. Due to its drug resistance it is known as a 'superbug' and is much more difficult to treat.
  • MRSA infections can have serious consequences including impacting the heart and lungs.
  • The best weapon against MRSA is to prevent its spread through the practice of good hygiene. Prevention is much better than treatment.
  • Thorough washing of your hands along with bandaging cuts can help to prevent transmission of MRSA.


  • “Methicillin-Resistant Staphylococcus Aureus (MRSA).” National Institute of Allergy and Infectious Diseases, U.S. Department of Health and Human Services,
  • “MRSA: Treatment, Causes, and Symptoms.” Medical News Today, MediLexicon International, 13 Nov. 2017,
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Your Citation
Bailey, Regina. "Methicillin-resistant Staphylococcus aureus (MRSA)." ThoughtCo, Jul. 29, 2021, Bailey, Regina. (2021, July 29). Methicillin-resistant Staphylococcus aureus (MRSA). Retrieved from Bailey, Regina. "Methicillin-resistant Staphylococcus aureus (MRSA)." ThoughtCo. (accessed June 1, 2023).