Methicillin-resistant staphylococcus aureus

Page last reviewed: 13/07/2011

MRSA stands for meticillin-resistant Staphylococcus aureus. Staphylococcus aureus (S. aureus or SA) is a bacteria or germ which many people carry in their nose or on their skin.

MRSA is a type of S. aureus that is resistant to a range of antibiotics including meticillin. 'Meticillin-resistant' means the bacteria cannot be killed by meticillin, a type of antibiotic that used to be able to kill them.

How do bacteria become resistant to antibiotics?

When bacterial infections are treated with antibiotics, some of them can survive. The surviving bacteria are able to mutate (change) and may develop a resistance to the antibiotic. Antibiotic resistance means that that antibiotics no longer works on that bacteria and no longer kills the bacteria. This means the bacteria are stronger, can multiply, and be ready to infect someone else.

This is how MRSA bacteria have become resistant to many antibiotics.

The number of antibiotic-resistant bacteria has increased in recent years due to:

  • people not finishing the full course of antibiotics they have been prescribed, which allows some bacteria to survive, to develop a resistance to the antibiotic and then multiply
  • antibiotics being overused, which has allowed bacteria to develop resistance to a wide range of antibiotics

MRSA can either be present harmlessly on the skin (colonisation) or enter the body (e.g. through broken skin) and cause an infection.

Colonisation

Staph aureus is commonly carried on the skin and in the nose of humans, where it mostly causes no harm. This is called colonisation. About one in every three people are colonised by Staph aureus in their noses, without any ill effects. Colonisation with Staph aureus (including MRSA) is NOT the same as infection.

Most people with MRSA carry the germ harmlessly and have no ill effects. The only way to tell if someone is carrying MRSA, or has an infection caused by MRSA, is to do a laboratory test on a sample from a wound, blood, urine, nose, or other part of the body. If MRSA is found in a sample it means that the person has MRSA on their body.

Infection

Infection is when a bacteria manages to get through the skin (for example through a cut) or into other parts of the body where it can multiply and cause a person to become ill. 

Screening for MRSA colonisation

Screening for MRSA colonisation means that a swab is rubbed over the area being tested (usually the inside of the nose, groin, armpit and areas of broken skin, if present) and sent to a laboratory.  This is a fast and painless procedure.  

In Ireland, national guidelines recommend that the following groups of patients are screened for MRSA colonisation:

1.     Patients known to have had MRSA before and who are being re-admitted to an acute hospital. 

2.     Patients transferred to one hospital from another hospital or health-care facility (e.g. nursing home)                    

3.     Patients admitted to hospital with non-intact skin, including wounds and ulcers.                                 

4.     Patients due to undergo certain types of surgery (e.g. cardiothoracic and vascular surgery, orthopaedic implant surgery

5.    Patients admitted to critical care areas, e.g. intensive care unit (ICU)

In general, the reasons patients are screened for MRSA are so that treatment can be given to clear the MRSA before certain types of surgery such as hip replacement surgery. It is also done to prevent MRSA spreading to other patients – if staff are aware that a patient is colonised with MRSA then they are usually placed in a single room

Decolonisation treatment consists of a range of treatments including:

  • A special body wash used when showering/bathing for a number of days
  • A cream that is applied to the inside of your nose

It is important that the specific instructions for decolonisation therapy should be followed.   

The treatment has few side effects. Generally, any side effects, such as skin irritation, will be mild. If you develop a rash, stop treatment and ask your clinic or doctor for advice

How does MRSA infection happen?

If MRSA  bacteria get into the body through a break in the skin, they can cause infections such as boils, an abscess or impetigo. If they get into the bloodstream they can cause more serious infections, such as blood poisoning (see MRSA infection - symptoms).

Who is most at risk of infection?

MRSA will not normally infect a healthy person. Although it is possible for people outside hospital to become infected, MRSA infections are most common in people who are already in hospital. This is because:

  • they often have an entry point for the bacteria to get into their body, such as a surgical wound, drip or a catheter
  • they tend to be older, sicker and weaker than the general population, which makes them more vulnerable to infection
  • they are surrounded by a large number of other patients and staff, so the bacteria can spread easily (through direct contact with other patients or staff, or via contaminated surfaces)

. The following are considered to be important risk factors forMRSA infection:

  • Age (older age groups are more prone)
  • Gender (males are twice-more at risk than females)
  • Prolonged hospital stay
  • Patients in intensive care, surgical and burns units
  • Patients with diabetes and other chronic conditions
  • Patients treated with broad-spectrum antibiotics  

Useful Links:

MRSA infection - treatment

Page last reviewed: 13/07/2011

Symptoms of MRSA infection

MRSA is a germ, therefore it itself does not have symptoms – the symptoms of an MRSA infection will depend on what part of the body is infected. For example a person with an MRSA skin infection will have skin infection symptoms and a person with an MRSA bloodstream infection will have symptoms of a bloodstream infection. MRSA can infect a range of body tissues and organs.

Skin infection

Most Staphylococcus aureus (SA) infections are skin infections, including:

  • boils (infections of the hair follicles)
  • abscesses (pockets of pus under the skin)
  • styes (infection of the eyelid glands)
  • carbuncles (large pus-filled lumps under the skin)
  • cellulitis (infection of the deep layer of the skin and the fat and tissues that lie beneath)
  • impetigo (a highly contagious skin infection that produces blisters)

You should keep an eye on minor skin problems like spots, cuts or burns. If you have a wound that becomes infected, see your doctor.

An MRSA-infected wound will become red, swollen and tender, with yellow pus seeping from it. Skin ulcers, such as pressure ulcers, are often sites of infection.

Bloodstream infection

If MRSA bacteria enter into the bloodstream from your skin, they can affect almost any part of the body. They can cause:

  • septicaemia (blood poisoning)
  • septic shock (widespread infection of the blood that leads to a fall in blood pressure and organ failure)
  • septic arthritis (severe joint problems)
  • osteomyelitis (bone marrow infection)
  • abscesses deep within the body
  • meningitis
  • pneumonia
  • endocarditis (infection of the heart lining)
GlossaryAbscesses
An abscess is a lump containing pus, which is made by the body during infection.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Bone marrow
Bone marrow is the soft, spongy tissue in the centre of bones that produces blood cells.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Tissues
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Page last reviewed: 13/07/2011

MRSA will not normally infect a healthy person. Although it is possible for people outside hospital to become infected, MRSA infections are most common in people who are already in hospital because:

  • They often have an entry point for the bacteria to get into their body, such as a surgical wound, a catheter or an intravenous tube. For example, if a patient colonised with MRSA bacteria touches their wound or catheter tube, they may infect themselves.
  • They tend to be older, sicker and weaker than the general population, which makes them more vulnerable to infection.
  • They are surrounded by a large number of other patients and staff, so the bacteria can spread easily.

How it spreads

MRSA bacteria are usually spread through skin-to-skin contact with someone who has an MRSA infection or who is colonised by the bacteria.

The bacteria can also spread through contact with towels, sheets, clothes, dressings or other objects that have been used by someone colonised or infected with MRSA.

During bed making, for example, skin scales from an infected or colonised person may become airborne and contaminate nearby surfaces.

MRSA can survive for long periods on objects or surfaces such as door handles, sinks, floors and cleaning equipment.

GlossaryAntibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Catheter
A catheter is a thin, hollow tube usually made of rubber that is placed into the bladder to inject or remove fluid.
Drip
A drip is used to pass fluid or blood into your bloodstream, through a plastic tube and needle that goes into one of your arteries or veins.
Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.
Intravenous
Intravenous (IV) means the injection of blood, drugs or fluids into the bloodstream through a vein.
Ulcer
An ulcer is a sore break in the skin, or on the inside lining of the body.

At-risk groups

Those most at risk of MRSA infection are those who:

  • have a weakened immune system, such as the elderly, newborn babies and those with a long-term health condition such as diabetes
  • have an open wound
  • have a catheter (a plastic tube inserted into the body to drain fluid) or an intravenous drip
  • have a burn or cut on their skin
  • have a severe skin condition such as leg ulcer or psoriasis
  • have recently had surgery
  • have to take frequent courses of antibiotics

Although MRSA infections usually develop in those being treated in hospital, particularly patients in intensive care units and on surgical wards, it is possible for hospital staff or visitors to become infected if they are in one of these higher-risk groups.

Page last reviewed: 13/07/2011

MRSA infections are diagnosed by testing blood, urine or a sample of tissue from the infected area for the presence of MRSA bacteria. If MRSA bacteria are found, further tests will be done to see which antibiotics the bacteria do not have resistance to, so that these can be used for treatment.

MRSA screening detects patients that are colonised with MRSA.  An MRSA screen usually involves a nasal and a groin swab (the swab looks like a cotton bud).

If you have been screened prior to hospital admision and found to be colonised with MRSA you will still be admitted, but doctors may give you treatment (decolonisation) to reduce or remove the MRSA bacteria. A person who has had MRSA in the past will have swabs taken to see if they are still carrying MRSA. They may be nursed in a single room, until the results of these swabs are known.

GlossaryAntibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Tissue
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Page last reviewed: 13/07/2011

MRSA infection can be treated  with antibiotics that the bacteria have not yet become resistant to.

Most MRSA infections can be treated with the following antibiotics:

  • Vancomycin or teicoplanin, which are normally given by injection or through a tube straight into your vein
  • Linezolid, which can be given into a vein or swallowed

Treatment for MRSA  may require an inpatient stay in an acute hospital.  You may be moved to a private room or to a room with others who have the bacteria, to stop the MRSA spreading. Some people will need to continue treatment for several weeks at home.

Visitors

MRSA does not usually harm healthy people. For example, it doesn't harm pregnant women or children, providing they are fit and healthy. Therefore, patients with  an MRSA infection will still be able to have visitors as normal.

However, it is essential that all visitors wash their hands thoroughly or use an alcohol hand rub before and after visiting

Some people are more at risk of MRSA. If you have an MRSA infection and someone who is at increased risk wishes to visit you in hospital, you should ask the hospital staff for advice before they visit.

GlossaryAntibiotic
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Antiseptic
Antiseptic is a substance that reduces the growth and development of germs.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.

If you are colonised with MRSA

If you are colonised with MRSA bacteria, you may need to be treated to get rid of the bacteria, particularly if you need to go into hospital for an operation. Before you are admitted, a special antibiotic bodywash will be applied to your skin and a cream to the inside of your nose, to remove the bacteria. You may also need to wash your hair with an antiseptic shampoo.

The treatment has few side effects. Generally, any side effects, such as skin irritation, will be mild. If you develop a rash, stop treatment and ask your clinic or doctor for advice.

Page last reviewed: 13/07/2011

How does MRSA  spread from person to person?

As with Staph aureus, MRSA is mainly spread by direct person-to-person contact (e.g. on unwashed hands) or through indirect contact by touching objects that have been contaminated with the bacteria. 

Hospital staff, patients and hospital visitors can take simple hygiene measures to help prevent the spread of MRSA and stop infection.

Hospital staff

Hospital staff who come into contact with patients should maintain very high standards of hygiene and take extra care when treating patients with MRSA:

  • Staff should thoroughly wash and dry their hands or use an alcohol hand gel/rub before and after touching  a patient, before an clean or aseptic procedure (e.g, giving an injection) and after touching any potentially contaminated equipment or dressings, after touching the patient surroundings (e.g., bed making)  and before handling food. 
  • Disposable gloves should be worn when staff  have physical contact with open wounds, for example when changing dressings, handling needles or inserting an intravenous drip. Hands should be cleaned  immediately after gloves are removed.
  • The hospital environment, including floors, toilets and beds, should be kept as clean and dry as possible.
  • Patients with a known or suspected MRSA infection should be isolated.
  • Patients should only be transferred between wards when this is strictly necessary.

The aim is to reduce the chance of patients infecting themselves and others.

For more information the Health Protection Surveillance Centre has produced the The Control of MRSA in Hospital and the Community which can be found on www.hpsc.ie

Patients

Hospital patients can reduce their risk of infection by taking the following sensible precautions:

  • Making sure they have soap, a flannel and moist hand wipes, as well as their own razor
  • Always washing their hands after using the toilet or commode (many hospitals now routinely offer a hand wipe)
  • Always washing their hands or cleaning them with a hand wipe immediately before and after eating a meal
  • Making sure their bed area is regularly cleaned and any unclean toilet or bathroom facilities reported to staff

Visitors

Visitors can reduce the chance of spreading MRSA to other people if they do not sit on the bed and if they clean their hands before and after entering the ward. They should use alcoholgel before touching the person they are visiting.

Dispensers of alcohol gel or hand rub are often placed by patients' beds and at the entrance to clinical areas.

For more information, see The Control of MRSA in Hospital and in the Community on www.hpsc.ie

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

Browse Health A-Z