MRSA (Methicillin-Resistant Staphylococcus Aureus) Infection

MRSA Staph Infection

What Is MRSA?

Staphylococcus aureus, often referred to simply as "staph," are bacteria commonly carried on the skin or in the nose of healthy people.

Sometimes, staph can cause an infection. In fact, staph bacteria are one of the most common causes of skin infections in the United States. Staph bacteria can also cause serious infections.

Some staph bacteria are resistant to antibiotics. One strain of staph resistant to certain antibiotics is MRSA. The acronym MRSA stands for methicillin-resistant Staphylococcus aureus. Methicillin is a type of antibiotic and was one of the first antibiotics that this particular strain of staph became resistant to. However, MRSA is now resistant to other types of antibiotics.

Types of MRSA

There are two types of MRSA, healthcare-associated MRSA and community-associated MRSA.

Until recently, MRSA was more likely to be a hospital-acquired infection. MRSA infections that are first acquired in the hospitals and healthcare facilities (such as nursing homes and dialysis centers) are known as healthcare-associated MRSA.

New strains of MRSA with unique microbiologic and genetic properties have recently emerged in the community and are capable of causing severe infections in otherwise healthy individuals. These MRSA infections are known as community-associated MRSA.

Over the past several decades, community-associated MRSA has become more common. This has escalated MRSA from a controllable condition (limited mostly to hospitals and healthcare facilities) to a serious public health concern.

Who Is at Risk?

Anyone can be at risk for community-associated MRSA. However, these infections do appear to occur more often in certain settings, such as schools, dormitories, military barracks, households, correctional facilities, and daycare centers.

These settings have factors that make it easier for MRSA to be transmitted, including:

Crowding
Frequent skin-to-skin contact
Compromised skin (i.e., cuts or abrasions)
Contaminated items and surfaces
Lack of cleanliness.

There are several factors that increase a person's chances of healthcare-associated MRSA. Some of these factors include:

A history of multiple hospitalizations
A recent hospitalization for a long period of time
Recent antibiotic use
Recent surgery
Having an IV line or bladder catheter
Having a weakened immune system from a medical condition (such as those with HIV or AIDS) or its treatment
Living in a nursing home or another long-term residence situation
Having dialysis for kidney failure.

(You can learn more about how MRSA is spread by clicking on MRSA Transmission. You can also learn who is at risk for MRSA by reading Who Is at Risk for Getting MRSA?)

How Is a MRSA Infection Transmitted?

MRSA transmission occurs between individuals through direct skin-to-skin contact or contact with shared items or surfaces that have come into contact with someone else's infection (such as towels or used bandages).

Not everyone who has MRSA will actually develop an infection. This is known as colonization. "Colonization" means that a person is carrying a specific type of bacteria, but does not have any signs or symptoms of illness that this particular bacteria type can cause. A person colonized with MRSA may also be called a MRSA "carrier."

It is estimated that up to 7 percent of people in hospitals and up to 2 percent of people in the community are colonized with MRSA, either on the skin or within their nose (the two most common areas). Although they do not have any signs or symptoms of MRSA, they can still infect others.

(See MRSA Transmission to learn more about how MRSA is spread and about colonization.)

Incubation Period

After a person has become infected with MRSA, it takes about 1 to 10 days on average for symptoms to appear. This period between MRSA transmission and the beginning of MRSA symptoms is called the "MRSA incubation period."

MRSA Signs and Symptoms

Common signs and symptoms of a MRSA infection can include a single red bump that resembles a pimple, pustule, or boil. It may also look like a cluster of red bumps. The involved site may also be red, swollen, warm, painful, and have pus or other drainage. MRSA is often confused with a spider bite in appearance.

MRSA skin infections commonly occur at sites of visible skin trauma (such as cuts and abrasions) and areas of the body covered by hair (such as the back of the neck, groin, buttocks, armpits, or beard area of men).

Community-associated MRSA can be particularly dangerous in children because their immune systems are not fully developed.

(Click Signs and Symptoms of a MRSA Infection to learn more.)

MRSA can cause more serious infections. Some of the most common areas that MRSA affects (and the types of infections caused) include the:

Lungs (pneumonia)
Bloodstream (bacteremia or septicemia)
Soft tissue (cellulitis)
Bone (osteomyelitis)
Inner lining of the heart (endocarditis).

These internal infections can cause serious and even life-threatening complications (see Complications of MRSA).

How Is It Diagnosed?

To diagnose MRSA, a sample is taken from the infection and sent to a lab for testing. If S. aureus (staph) is found, the organism will be further tested to determine which antibiotic is the most effective treatment.

There are newer tests that are becoming more widely available that can detect staph DNA in a matter of hours.

(Click Diagnosing MRSA to learn more.)

Treating a MRSA Infection

The recommended treatment for a MRSA infection will depend on such things as:

The severity of the infection
Test results (including which antibiotics will likely be the most effective)
Other existing medical conditions
The person's age.

For mild to moderate skin infections, your healthcare provider may insert a needle to remove some of the infected fluid or make a cut on the skin to drain the infection. This can help the tissue heal more quickly. It is very important that you do not try to do this yourself. Self-treatment can make things a lot worse. Antibiotics may also be prescribed for mild to moderate skin infections.

Treatment for serious MRSA infections may require hospitalization and IV antibiotics.

(Click MRSA Treatment to learn more about treating a MRSA infection. This article contains some considerations to be aware of while undergoing treatment for this infection.)

Prevention

Below are some other strategies to help prevent a MRSA infection:

Keep your hands clean by washing thoroughly with soap and water.
Always shower promptly after exercising.
Keep cuts and scrapes clean and covered with a bandage until healed.
Avoid contact with other people's wounds or bandages.
Avoid sharing personal items, such as towels, washcloths, razors, clothes, or uniforms.
Wash soiled sheets, towels, and clothes with water and laundry detergent; use bleach and hot water if possible.
Dry clothes in a hot dryer, rather than air-drying (helps kill bacteria in clothes).

(Click MRSA Prevention to learn more.)

The History of MRSA

Staphylococcus aureus, or S. aureus, is commonly known as "staph." This bacterium was discovered in the 1880s. During this era, S. aureus infections most often caused painful skin and soft tissue conditions, such as boils and impetigo.

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.

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.