Almost all MRSA infections acquired in hospital are caused by healthcare-acquired strains (HCA-MRSA) which mainly affect those with reduced immunity. This includes elderly and immunocompromised patients, particularly those with wounds, damaged skin or indwelling devices.
Although most of these MRSA infections arise in hospitals, the organism can also affect the elderly and immunocompromised in a home-care setting. As it spreads in the community, increasing numbers of vulnerable people are at risk of colonisation or infection.
A key measure in controlling MRSA infections is therefore the prevention of the spread of this organism in the home and community.
Community-acquired strains (CA-MRSA) have also emerged that affect mainly young, healthy people and children. CA-MRSA has become a major problem in the USA, but is still relatively uncommon in the UK.
A particular problem with CA-MRSA is that some strains produce the Panton-Valentine-Leukocidin (PVL) toxin. Skin and soft tissue infections that start out looking like an insect bite can rapidly progress to boils and deep-seated abscesses.
Data are limited but around 2 per cent of UK MRSA strains may be PVL-positive, although the figure may be much higher. CA-MRSA strains are only resistant to a limited spectrum of antibiotics and are easily treated once the nature of the infection has been identified.
Any family member is at risk of infection with CA-MRSA, although US experience suggests that these strains affect mainly those who engage in activities involving close skin contact and abrasion, such as contact sports.
Spread of MRSA
Carriage of MRSA in the community is low, with recent estimates suggesting it is around 0.5-3 per cent.
It is mostly found in the elderly and those recently in healthcare institutions, although healthcare workers can also become carriers as a result of contact with their patients. The relative prevalence of CA-MRSA to HCA-MRSA carriage is unknown.
MRSA is a robust organism that can easily be transmitted between hands, surfaces and fabrics. It can be spread by asymptomatic carriers as well as infected people. It is shed mainly from the skin surface, usually on skin scales, although it may also be shed from the nose. Household pets can also act as carriers.
When infected patients are discharged from hospital, MRSA can be transmitted to other family members, or spread around the home where it can survive for significant periods. The patient can recover, but then be re-infected by family members or pets who are now carriers, or by contaminated environmental surfaces.
In the longer term, MRSA can be controlled by prudent antibiotic prescribing that reduces the pressure driving the emergence of antibiotic-resistant strains.
In 2007, the Advisory Committee on Antimicrobial Resistance (SACAR) published prescribing guidelines for antibiotic treatment and prophylaxis.
Control of MRSA hinges on good hygiene. In 2006, in response to concerns about the circulation of pathogens such as Clostridium difficile and MRSA in the community, the International Scientific Forum on Home Hygiene (IFH) prepared a report evaluating the implications of spread in the community as opposed to healthcare settings.
The IFH also produced hygiene advice sheets for GPs. These give advice about steps patients should take to reduce the spread of MRSA when a family member is infected, and what they should do to reduce day-to-day spread of MRSA.
Hygiene measures to break the chain of MRSA transmission in the home are based on the IFH 'targeted hygiene' concept, which focuses intervention on the times, places and situations of greatest risk.
Critical control points are hands, together with hand contact surfaces, cleaning cloths and cleaning utensils. These form the 'superhighways' by which MRSA is spread around the home, exposing healthy family members to infection.
MRSA can survive on dry surfaces and so it is important that clothing, particularly sports clothes, and household linens are regularly washed under conditions which eliminate MRSA.
They should be laundered either at 60 degress or at 40 degrees celsius using a bleach-containing laundry product.
Family members should not share towels, toothbrushes or other personal items.
Good personal hygiene with regular cleaning of baths, basins and shower surfaces will also reduce spread of MRSA. Daily vacuuming is recommended in homes where there is high risk of infection.
Wound care in the home is particularly important. Covering infected wounds reduces the risk to others of infection from the wound.
In healthy family members, applying an antiseptic cream to cuts and covering them with an impermeable dressing can help prevent infection.
Targeted hygiene also means hygienic cleaning of risk surfaces at appropriate times to interrupt the chain of MRSA transmission.
Hygienic cleaning involves either detergent-based cleaning with rinsing, or using a disinfectant/cleanser that inactivates MRSA in situ.
In many situations a 'hygienically clean' surface can be achieved by soap and water alone, although recent studies suggest that this process is only effective if accompanied with thorough rinsing.
Wiping a surface with a cloth moves the bacteria around the surface and onto the cloth and hands, from where they can be transferred to other surfaces.
We should therefore not be afraid to recommend using a disinfectant. Waterless hand sanitisers should also be recommended for situations where access to soap and water is limited.
The spread of MRSA needs to be addressed not only in healthcare facilities but also in the community. There has been an emphasis on 'patient empowerment' strategies to reduce infections in hospitals, but evidence suggests that this is not enough.
Hospital managers now realise that one of the keys to reducing MRSA in hospitals is to reduce the number of 'silent' or infected patients (or visitors or healthcare workers) who enter their hospital - which in turn means reducing the spread of MRSA in the community.
In recent years hygiene has had a somewhat negative image. We need to change this perception and make good hygiene more appealing to the public by associating it with health and well-being.
However, persuading the public that they need to share responsibility for preventing the spread of infection, without being accused of shifting the blame may be a challenge.
Professor Bloomfield is a consultant in hygiene and infectious disease prevention, chairman and member of the scientific advisory board of the IFH and honorary professor at the London School of Hygiene and Tropical Medicine
- S F Bloomfield, B D Cookson, F R Falkiner, et al. Methicillin resistant Staphylococcus aureus (MRSA), Clostridium difficile and ESBL-producing Escherichia coli in the home and community: assessing the problem, controlling the spread. (2006)
- Methicillin resistant Staphylococcus aureus (MRSA) and the home: Briefing document and advice sheet.