What Is MRSA?
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Medically reviewed by Anju Goel, MD, MPH
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of infection-causing bacterium that is resistant to the antibiotic methicillin (meaning it cannot be treated with methicillin) and sometimes other antibiotics as well. Because it is resistant to one or more antibiotics, MRSA infections can be more complicated to treat than infections caused by bacteria that are not antibiotic resistant.
About one in three people carry the Staphylococcus aureus bacteria that causes MRSA infection on their skin. About two out of every 100 people carry MRSA. For most people, this doesn’t cause any issues; however, if this bacteria spreads uncontrollably, then symptoms start to arise. Other types of infections caused by MRSA, like skin infections, are more prevalent than bloodstream infections, sometimes called bacteremia.
MRSA infections have similar symptoms to other bacterial infections, including swelling, redness, or fever, and depend on where the infection is in the body. It is also treated with antibiotics, although which antibiotics can be used is limited. Many MRSA infections can be prevented with proper hygiene and protection measures.
Older adults, nursing home residents, people with organ dysfunction (such as kidney failure or heart failure), or people with weakened immune systems are at an increased risk of getting a MRSA infection. Extra precautions may be needed to protect these groups.
Types
Primarily, there are two types of MRSA infection. These are categorized based on where the infection has been acquired. The two types—hospital-acquired and community-acquired—may have differences in terms of how they look and act, which can affect treatment.
Hospital-Acquired MRSA
Hospital-acquired MRSA (HA MRSA) infection, as the name suggests, is picked up in healthcare facilities and nursing homes. This type was originally identified among hospitalized patients in 1961, and primarily affects those who have weakened immune systems. It is typically severe and difficult to manage. HA MRSA tends to spread from the skin to the blood, bones, or other organs, such as the heart, lungs, and brain.
Community-Acquired MRSA
MRSA infection that arises outside of hospitals, clinics, or nursing homes is called community-acquired MRSA (CA MRSA). It most often spreads in places like gym locker rooms, day care facilities, military barracks, or other areas where people are in close quarters. First isolated in the late 1980s, CA MRSA infection is primarily seen in the skin, though it also can affect the lungs. Unlike HA MRSA, this type can affect people with healthy immune systems.
MRSA Symptoms
MRSA symptoms will differ from person to person depending on where in the body the infection is located. When someone gets it outside of a healthcare setting, MRSA most often shows up as a skin infection. Sometimes, MRSA may confused at first for a spider bite, especially if there is no obvious injury that is the source of the infection. Signs of MRSA in the skin include:
A single, tender, red, raised lump
A group of small, raised lumps that look like pimples
A large lump that is tender and drains pus (sometimes called a carbuncle)
CA MRSA infection most commonly causes these issues, which include:
Cellulitis: This is a common infection that causes red, painful, and swollen areas of the skin.
Necrotizing fasciitis: A rarer, severe, and quickly spreading infection, necrotizing fasciitis causes blisters on the skin, unhealing wounds, and pain, alongside fever; this condition can be fatal.
Foot ulcers: Another skin symptom is the development of persistent open sores and wounds that don’t heal on the feet.
MRSA can cause pneumonia, an infection that causes the lungs to fill with fluid or pus. It can also cause issues with the bone and joints; this includes osteomyelitis, which is characterized by inflammation and swelling of the bones, including the spine or the longer bones of the arms or legs; and arthritis, which causes painful swelling and loss of mobility in the joints.
Once it gets to the blood, the infection can spread to areas such as heart valves or medical devices like pacemakers or replacement joints. In these cases, symptoms can include swelling and pain in the infected area as well as more general signs of infection like fatigue and fever.
Occasionally, people may have a MRSA infection but not have any symptoms. They can still transmit the bacterium to another person who could become infected.
What Causes MRSA?
A MRSA infection occurs when a methicillin-resistant version of the bacterium Staphylococcus aureus enters an open area in your skin, such as from a cut, scrape, or burn.
Around a third of people carry Staphylococcus aureus on their skin or in their nose without being infected with it. This is called being "colonized". It's not known exactly how many people colonized with Staphylococcus aureus carry the methicillin-resistant kind.
Most of the time, someone becomes infected with MRSA when they come in direct physical contact with someone else colonized or infected with MRSA. Occasionally, someone may become infected by having indirect contact with a colonized person such as coming in contact with their towels, sheets, wound dressings, or workout equipment. You are much more likely to get MRSA from someone with an active infection than someone who is a carrier.
Some people are more likely to develop a MRSA infection. Risk factors can include:
Recently taking antibiotics
Having a surgical wound, intravenous line (IV), or central line
Staying in the hospital for long periods of time
Having a weakened immune system
Having direct contact with people colonized with MRSA
Having open areas of skin like sores, burns, scrapes
Being an athlete who plays on a team
Having tattoos or piercings or removing body hair by shaving or waxing
People who use injection drugs
People in daycare centers
People in prison
Diagnosis
If your healthcare provider suspects you may have a MRSA infection, the tests they may run to confirm it will vary depending where the infection is in your body. Samples from blood, sputum (spit), urine, or scrapings from a wound can all be sent to a lab and be tested for MRSA.
People who have a MRSA infection in a location inside their body like the lungs, joints, or bones, may need some sort of imaging as well as bloodwork to confirm the presence and location of the infection. Imaging could include:
X-rays
Echocardiograms
Treatments for MRSA
The most common treatment for MRSA is antibiotics. Your provider may be able to tailor which antibiotic will be most effective for killing the bacteria based on the results of your lab cultures. If you are at home, you will likely take antibiotics in the form of pills for around 7-10 days. If you are in the hospital during your treatment you will likely receive IV antibiotics. You may continue to have either IV or oral antibiotics for days to weeks after hospitalization.
If your provider prescribes antibiotics it is important to take the medication as instructed for the full length of time the provider recommends, even if you are feeling better.
If you have a skin infection, your provider may drain any build-up of pus, either by inserting a needle or by making a small cut for drainage. This procedure may help your tissue to heal by getting rid of the dead, infected material in the pus as well as reduce pain by removing the pressure of the build-up of pus under the skin. It is important that you let a healthcare provider do this and not attempt to do it on your own as that could lead to an increased risk of a new infection forming.
Prevention
Like most infections, MRSA is largely preventable, both at home and in the healthcare setting. Some ways to prevent becoming infected with MRSA include:
Frequently wash your hands with soap and water
Keep any openings in the skin like scratches, wounds, or burns clean and covered until they are healed
Avoid sharing personal items like towels, razors, or clothing
Wash soiled sheets, clothes, or towels in hot water with laundry detergent and then dry them with hot air to help kill bacteria
Frequently clean household surfaces like counters and sinks, especially if someone in the house has an infection
Speaking to a healthcare provider as soon as you suspect you have an infection can prevent it from getting worse
Complications
If MRSA gets into the bloodstream it can cause a serious complication called sepsis. Sepsis is the body's extreme reaction to infection and is life-threatening. Signs and symptoms for sepsis include:
High heart rate
Weak pulse
Confusion
Fever, chills, or sweating
Extreme pain
Clammy skin
Shortness of breath
If you believe you are experiencing signs of sepsis, it is important to either go to the emergency room or call 911 right away. Sepsis can be treated, but needs hospitalization to properly manage it.
A Quick Review
MRSA can cause serious infections, but often it responds well to antibiotic treatment. Some people in the United States are colonized with MRSA and may not even know it.
MRSA can lead to deadly complications like sepsis, and certain groups like seniors, nursing home residents, and people with organ dysfunction have higher mortality rates with MRSA infection.
Although it is a dangerous infection, there are many steps people can take both in the healthcare setting and the community to prevent MRSA infections and keep themselves safe.
Frequently Asked Questions
How long is a person contagious with MRSA?
People can spread MRSA as long as they carry it. However, people with active infections are much more contagious than someone who is merely colonized (sometimes called a carrier).
Can MRSA live on bedding?
Yes, MRSA can live on bedding. If there is any visible wound drainage or bodily fluids on the sheets from a person with MRSA, they should be washed with hot water and detergent or warm water and bleach and make sure items are fully dry before using again.
How fast does MRSA spread?
MRSA can progress quickly. The time between first coming in contact with the bacterium and the first signs of infection is typically 4-10 days.
What happens if MRSA goes untreated?
If a MRSA infection goes untreated it may spread and progress to serious complications like sepsis and death.
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