Methicillin-resistant Staphylococcus aureus (MRSA) is a type of Staphylococcus aureus infection that is resistant to all beta-lactam antibiotics.
- Methicillin-resistant strains of Staphylococcus aureus (MRSA) were first recognized in 1961, one year after the antibiotic methicillin was introduced for treating S. aureus infections.
- MRSA is resistant to (unable to be killed by) all beta-lactam antibiotics. This includes all penicillins (e.g., amoxicillin) and cephalosporins (e.g., keflex).
- The first documented MRSA outbreak in the United States occurred at a Boston hospital in 1968.
- For the next two decades most MRSA infections occurred in persons who had contact with hospitals or other health care settings (health care-associated MRSA).
- However, MRSA infections are now seen in previously healthy persons.
- These persons appear to have acquired their infections in the community (community-associated MRSA), rather than in a health care setting.
- S. aureus is most often spread to others by contaminated hands.
- The skin and mucous membranes are usually an effective barrier against infection. However, if these barriers are breached (e.g., skin damage due to trauma or mucosal damage due to viral infection) S. aureus may gain access to underlying tissues or the bloodstream and cause infection.
- Persons who are immunocompromised or who have invasive medical devices are particularly vulnerable to infection.
- Traditionally, Methicillin-resistant Staphylococcus aureus (MRSA) infections have been associated with hospitalization or other health care-associated risk factors.
- Healthcare-associated MRSA (HA-MRSA)
More information about causes and transmission of HA-MRSA.
- In recent years physicians and other health care providers have observed an increasing number of people with MRSA infections who lack traditional health care-associated risk factors. These people appear to have community-associated infections.
- Community-associated MRSA (CA-MRSA)
More information about history, transmission, and causes of CA-MRSA.