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About one in three of us carries SA on the surface of our skin, or in our nose, without developing an infection. This is known as being colonised by the bacteria. However, if SA bacteria get into the body through a break in the skin they can cause infections such as boils, abscesses or impetigo. If they get into the bloodstream they can cause more serious infections.
Most SA infections can be treated with antibiotics such as methicillin (a type of penicillin). However, SA is becoming increasingly resistant to most commonly used antibiotics. MRSA bacteria are those types of SA bacteria that are resistant to methicillin (and usually to some of the other antibiotics that are normally used to treat SA infections).
MRSA is no more infectious than other types of SA bacteria. However, MRSA infections are more difficult to treat due to the antibiotic resistance of the bacteria. Antibiotics can still be used to treat MRSA, the infection may simply require a much higher dose over a much longer period, or the use of an antibiotic to which the bacteria is not resistant.
Symptoms of MRSA
Staphylococcus aureus (SA) bacteria are common, and about one in three people are colonised by the bacteria. Most of those who are colonised with SA do not develop an infection and so do not have any symptoms.
However, if SA bacteria are able to enter the body they can cause infection. The symptoms will depend on the type of infection they cause.
Most SA infections are skin infections, including:
- boils (pus-filled infections of hair follicles),
- abscesses (collections of pus in pockets under the skin),
- styes (infection of glands in the eyelid),
- carbuncles (infections larger than an abscess, usually with several openings to the skin),
- cellulitis (infection of the skin and the fat and tissues that lie immediately beneath it), and
- impetigo (a skin infection that produces pus-filled blisters).
You should keep an eye on minor skin problems like spots, cuts or burns. If you have a wound that becomes infected you should see your doctor.
Although most SA infections are skin infections, if SA bacteria are able to enter the bloodstream (bacteraemia) 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),
- severe joint problems (septic arthritis),
- bone marrow infection (osteomyelitis),
- internal abscesses anywhere within the body,
- inflammation of the tissues that surround the brain and spinal cord (meningitis),
- lung infection (pneumonia), and
- infection of the heart lining (endocarditis).
SA bacteria can also cause scalded skin syndrome and, very occasionally, toxic shock syndrome.
Causes of MRSA
When bacteria encounter an antibiotic, such as methicillin, some of the bacteria may survive. Bacteria are able to mutate (change), so those bacteria that survive may develop a resistance to the antibiotic. The surviving antibiotic-resistant bacteria can then multiply, ready to infect someone new. In this way, some types of staphylococcal aureus bacteria have become resistant to many antibiotics, forming MRSA.
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, develop a resistance to the antibiotic, and then multiply, and
- antibiotics being overused, which has allowed bacteria to develop resistance to a wide range of antibiotics.
MRSA bacteria is usually spread through person-to-person contact with someone who has an MRSA infection, or who is colonised by the bacteria. It can also spread through contact with towels, sheets, clothes, dressings or other objects that have been used by someone with MRSA. MRSA can also survive on objects or surfaces such as door handles, sinks, floors and cleaning equipment.
MRSA will not normally cause an infection in a healthy person. Although it is possible for those outside hospital to become infected, MRSA infections are most common in people who are already in hospital. Those in hospital are more likely to develop MRSA infections 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.
Those who are most at risk of MRSA include those who have:
- a weakened immune system, such as the elderly, newborn babies, or those with a long-term health condition such as diabetes, cancer or HIV/AIDS,
- an open wound,
- a catheter (a plastic tube inserted into the body to drain fluid) or an intravenous drip,
- a burn or cut on their skin,
- a severe skin condition such as leg ulcer or psoriasis,
- recently had surgery, or
- 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.
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, and so which can be used to treat them.
Many hospitals now test everyone who is being admitted to see if they are colonised with MRSA. Swabs from the skin and nose, urine and blood samples may be tested for the bacteria. It can take 3-5 days for the results to come back.
If you are colonised with MRSA you will still be admitted, but doctors may give you treatment to reduce or remove the MRSA bacteria.
Treatment of MRSA depends on whether you are infected with Staphylococcus aureus (SA) bacteria, or only colonised. You are considered to be infected with MRSA if the bacteria have entered your bloodstream, such as through a break in your skin. However, if you have SA bacteria on the surface of your skin without developing an infection, you are said to be colonised.
If you have an MRSA infection, you will be given antibiotics that are still effective and a type that the bacteria have not yet become resistant to. Most MRSA infections can be treated with the antibiotics vancomycin, or linezolid, which are normally given through injection or intravenously (through a tube straight into your vein). Most MRSA infections will require treatment in hospital and antibiotic treatment may need to continue for several weeks.
If you are colonised with MRSA bacteria, you may be treated, particularly if you need to go into hospital for a procedure such as an operation. If you have a local or serious MRSA infection, you may need to continue having treatment when you go home.
If you require treatment to remove MRSA bacteria before going into hospital, before being admitted, a special antibiotic cream will be applied to your skin, or to the inside of your nose, to remove the bacteria. You may also need to wash your skin and hair with an antiseptic shampoo and lotion.
If you are in hospital and you have an MRSA infection, you may be moved to a private room or to a room with others who have the bacteria, to stop MRSA spreading.
MRSA does not normally cause harm to healthy people (it cannot harm pregnant women, children or babies, providing they are fit and healthy), so if you have an MRSA infection you will still be able to have visitors as normal. However, it is essential that all visitors wash their hands thoroughly before and after visiting every patient. Fast-acting, special alcohol rubs or gels are used in most hospitals, with dispensers usually located by patients' beds.
Some people are more at risk of MRSA (see the Causes section). 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.
If you are prescribed antibiotics you should always make sure that you complete the full course.
MRSA is usually passed on by human contact, often from the skin of the hands. You should always wash your hands thoroughly before and after visiting someone in hospital.
Hospital staff who come into contact with patients should maintain very high standards of hygiene and take extra care when treating patients with MRSA. Before and after caring for any patient, hospital staff should make sure they have thoroughly washed and dried their hands. Many hospitals now use fast-acting, special antiseptic solutions, like alcohol rubs or gels - you may find dispensers placed by patients beds and at the entrance to clinical areas for use by staff and visitors. Staff should wear disposable gloves when they have physical contact with open wounds, for example when changing dressings, handling needles or inserting an intravenous drip.
If you are concerned about hygiene, do not be afraid to ask the doctor or nurse treating you, or your visitors, if they have washed their hands.
If you are in hospital, you can reduce your risk of infection by taking the following sensible precautions.
- Keep your hands and body clean. Take soap, a flannel and moist hand-wipes with you, as well as your own razor.
- Always wash your hands after using the toilet or commode (many hospitals now routinely offer a hand-wipe).
- Always wash your hands or clean them with a hand-wipe immediately before and after eating a meal.
- Make sure your bed area is regularly cleaned and report any unclean toilet or bathroom facilities to staff.
NHS Choices links
- News: resistant E. coli
- News: antibiotic resistance
- News: MRSA screening
- Health A-Z: clostridium difficile
- Health A-Z: antibiotics
- Health A-Z: abscess
- Health A-Z: impetigo
- Health A-Z: septic shock
- Health A-Z: pneumonia