Methicillin-resistant Staphylococcus aureus (MRSA)

MRSA is an important cause of infection in both healthy people in the community and in patients in healthcare institutions.

It is important to distinguish MRSA colonization from infection.

Healthcare-associated MRSA infections and community-associated MRSA infections exhibit important differences in antibiotic susceptibility.

Community-associated MRSA most commonly results in skin and soft-tissue infections and therapy can often be with oral antibiotics.

Healthcare-associated MRSA infections usually require treatment with intravenous antibiotics.

Isolation of patients with MRSA, through contact precautions, may help to prevent spread of infection.

MRSA is a type of Staphylococcus aureus that is resistant to most beta-lactam antibiotics, antistaphylococcal penicillins (e.g., methicillin, oxacillin), and cephalosporins. Methicillin resistance is defined as an oxacillin minimum inhibitory concentration of ≥4 micrograms/mL.[1]Babel BS, Decker CF. Microbiology and laboratory diagnosis of MRSA. Dis Mon. 2008 Dec;54(12):769-73. http://www.ncbi.nlm.nih.gov/pubmed/18996278?tool=bestpractice.com Oxacillin is in the same class as methicillin and was chosen as the agent for testing of S aureus sensitivity in the early 1990s. Methicillin is still used to describe resistance because of its historical role.[2]Centers for Disease Control and Prevention. Laboratory detection of oxacillin/methicillin-resistant Staphylococcus aureus. May 2019 [internet publication]. http://www.cdc.gov/HAI/settings/lab/lab_mrsa.html MRSA infections can include syndromes of bacteremia, pneumonia, endocarditis, joint infections, and skin or soft-tissue infections.