Community-Associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA)


Antibiotic resistance in Staphylococcus aureus has been a growing problem since penicillin was first introduced in the 1940s. Staphylococcal penicillin resistance developed in the 1950s, followed by methicillin resistance in the 1970s, but methicillin resistance was largely found in hospitals and not in the community. Since the late 1990s, MRSA has become a widespread cause of disease in the community, associated with the emergence of a new and virulent strain known as USA-300. During the first few years of this century, CA-MRSA spread rapidly in Georgia and is now a widespread and common cause of infections.

Community-associated MRSA (CA-MRSA) can affect otherwise healthy individuals with no exposure to settings where antibiotic resistance is expected, like hospitals. CA-MRSA frequently causes skin or soft-tissue infections that contain pus. Most of these are uncomplicated and easily treated, but some CA-MRSA infections are severe, including sepsis, pneumonia, osteomyelitis (bone infection) or endocarditis (heart-valve infection). This strain is also becoming established in hospitals.

In the 8-county Atlanta MSA, the Emerging Infections Program conducts active, laboratory-based surveillance for all cases of MRSA, and classifies them as either community-associated, healthcare-associated community-onset, or healthcare-associated hospital-onset. This surveillance system, although limited geographically, is considered to be a gold standard for quantitative information over time.

Vaccination & Prevention

There is no vaccine to prevent S. aureus infections. Because S. aureus are typically carried in the nose and on the skin, general prevention measures include covering coughs and sneezes, good hand hygiene, and covering open wounds to prevent contamination. Personal items that contact skin (such as towels, razors, or bar soap) should not be shared. Antibiotic use promotes carriage of and infection with bacteria that are antibiotic-resistant. Unnecessary antibiotics should be avoided for this and other reasons, such as cost, side-effects, and allergies.

Following multiple outbreak investigations, CDC has characterized risk factors ("the 5 C's") associated with CA-MRSA disease, which include Crowding, Close contact, Compromised skin, Contaminated surfaces and shared personal items, lack of Cleanliness, and in some outbreaks, prior antimicrobial use.

More about MRSA:

For Healthcare Providers:

Additional Resources:


Updated 12/27/2022