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S. Aureus
Read about how NIAID-Funded Researchers Discover an Additional Way that S. Aureus Evades Immune System Attacks.

Antimicrobial (Drug) Resistance

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Methicillin-Resistant Staphylococcus aureus (MRSA)

History

The Staphyloccoccus aureus bacterium, commonly known as staph, was discovered in the 1880s. During this era, S. aureus infection commonly caused painful skin and soft tissue conditions such as boils, scalded-skin syndrome, and impetigo. More serious forms of S. aureus infection can progress to bacterial pneumonia and bacteria in the bloodstream—both of which can be fatal. S. aureus acquired from improperly prepared or stored food can also cause a form of food poisoning

In the 1940s, medical treatment for S. aureus infections became routine and successful with the discovery and introduction of antibiotic medicine, such as penicillin.

From that point on, however, use of antibiotics—including misuse and overuse—has aided natural bacterial evolution by helping the microbes become resistant to drugs designed to help fight these infections.

In the late 1940s and throughout the 1950s, S. aureus developed resistance to penicillin. Methicillin, a form of penicillin, was introduced to counter the increasing problem of penicillin-resistant S. aureus. Methicillin was one of most common types of antibiotics used to treat S. aureus infections; but, in 1961, British scientists identified the first strains of S. aureus bacteria that resisted methicillin. This was the so-called birth of MRSA.

The first reported human case of MRSA in the United States came in 1968. Subsequently, new strains of bacteria have developed that can now resist previously effective drugs, such as methicillin and most related antibiotics.

MRSA is actually resistant to an entire class of penicillin-like antibiotics called beta-lactams. This class of antibiotics includes penicillin, amoxicillin, oxacillin, methicillin, and others.

S. aureus is evolving even more and has begun to show resistance to additional antibiotics. In 2002, physicians in the United States documented the first S. aureus strains resistant to the antibiotic, vancomycin, which had been one of a handful of antibiotics of last resort for use against S. aureus. Though it is feared that this could quickly become a major issue in antibiotic resistance, thus far, vancomycin-resistant strains are still rare.

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Last Updated March 04, 2008

Last Reviewed March 04, 2008