Methicillin-resistant Staphylococcus aureus, or MRSA, is the result of a type of bacterial infection that affects the skin. This infection received its name after scientists discovered that Staphylococcus aureus bacteria had developed a resistance to the antibiotic (methicillin) used to treat the bacteria. MRSA can cause painful skin and soft tissue problems, such as boils, scalded-skin syndrome, and impetigo. It can also cause serious conditions, such as blood infections or pneumonia.
What Causes MRSA?MRSA is a strain of the bacteria Staphylococcus aureus. MRSA is actually short for methicillin-resistant Staphylococcus aureus. Methicillin is a type of antibiotic that was commonly used to treat infections. MRSA is resistant to this type of antibiotic, along with other similar antibiotics.
Over the past several decades, MRSA has gone from being a controllable condition limited mostly to hospitals and healthcare facilities (such as nursing homes and dialysis centers), to a serious public health concern.
In fact, new strains have recently emerged in the community that are capable of causing severe infections in otherwise healthy individuals. These MRSA infections are known as community-associated MRSA. MRSA infections that are acquired in the hospitals and healthcare facilities are known as healthcare-associated MRSA.
Understanding the MRSA Cause Begins With the HistoryStaphylococcus aureus, or S. aureus, is commonly known as "staph." This bacterium was discovered in the 1880s. During this era, S. aureus infections commonly caused painful skin and soft tissue conditions, such as boils, scalded-skin syndrome, and impetigo. It was also known to occasionally progress to very serious infections in the blood or lead to pneumonia.
In the 1940s, medical treatment for S. aureus infections became routine and successful with the discovery and introduction of antibiotic medication, such as penicillin.
From that point on, however, the 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 the most common types of antibiotics used to treat S. aureus infections. However, 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 occurred in 1968. Subsequently, new strains of bacteria have developed that can now resist previously effective drugs, such as methicillin and most related antibiotics. This includes antibiotics such as oxacillin, penicillin, amoxicillin (Amoxil®), 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 (Vancocin®), 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 at this time.
(Click Who Is at Risk for Getting MRSA? to learn more about the risk factors for MRSA.)