MRSA

Methicillin-resistant Staphylococcus aureus; Community-acquired MRSA (CA-MRSA); Hospital-acquired MRSA (HA-MRSA)

Last reviewed: May 30, 2009.
U.S. National Library of Medicine
National Institutes of Health

National Center for Biotechnology Information U.S. National Library of Medicine National Institutes of Health Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial infection that is highly resistant to some antibiotics.

MRSA is a strain of Staphylococcus aureus (S. aureus) bacteria. S. aureus is a common type of bacteria that normally live on the skin and sometimes in the nasal passages of healthy people. MRSA refers to S. aureus strains that do not respond to some of the antibiotics used to treat staph infections.

The bacteria can cause infection when they enter the body through a cut, sore, catheter, or breathing tube. The infection can be minor and local (for example, a pimple), or more serious (involving the heart, lung, blood, or bone).

Serious staph infections are more common in people with weak immune systems. This includes patients in hospitals and long-term care facilities and those receiving kidney dialysis.

MRSA infections are grouped into two types:

  • Healthcare-associated MRSA (HA-MRSA) infections occur in people who are or have recently been in a hospital or other health-care facility. Those who have been hospitalized or had surgery within the past year are at increased risk. MRSA bacteria are responsible for a large percentage of hospital-acquired staph infections.
  • Community-associated MRSA (CA-MRSA) infections occur in otherwise healthy people who have not recently been in the hospital. The infections have occurred among athletes who share equipment or personal items (such as towels or razors) and children in daycare facilities. Members of the military and those who get tattoos are also at risk. The number of CA-MRSA cases is increasing.

 

Symptoms

Staph skin infections cause a red, swollen, and painful area on the skin. Other symptoms may include:

  • Drainage of pus or other fluids from the site
  • Fever
  • Skin abscess
  • Warmth around the infected area

Symptoms of a more serious staph infection may include:

  • Chest pain
  • Chills
  • Cough
  • Fatigue
  • Fever
  • General ill feeling (malaise)
  • Headache
  • Muscle aches
  • Rash
  • Shortness of breath

Researchers in Italy and the U.K. tested five major marihuana chemicals called cannabinoids on different strains of MRSA (methicillin-resistant Staphylococcus aureus). All five showed germ-killing activity against the MRSA strains in lab tests. Some synthetic cannabinoids also showed germ-killing capability. The scientists note the cannabinoids kill bacteria in a different way than traditional antibiotics, meaning they might be able to bypass bacterial resistance.

At least two of the cannabinoids don’t have mood-altering effects, so there could be a way to use these substances without creating the high of marihuana.

MRSA, like other staph infections, can be spread through casual physical contact or through contaminated objects. It is commonly spread from the hands of someone who has it. This could be in a health care setting, though there have also been high-profile cases of community-acquired MRSA.

It is becoming more common for healthy people to get MRSA, which is often spread between people who have close contact with one another, such as members of a sports team. Symptoms often include skin infections, such as boils. MRSA can become serious, particularly for people who are weak or ill.

In the study, published in the Journal of Natural Products, researchers call for further study of the antibacterial uses of marihuana. There are “currently considerable challenges with the treatment of infections caused by strains of clinically relevant bacteria that show multi-drug resistance,” the researchers write. New antibacterials are urgently needed, but only one new class of antibacterial has been introduced in the last 30 years. “Plants are still a substantially untapped source of antimicrobial agents,” the researchers conclude.