Online-only article: Preventing MRSA infection

Written by Dr Beryl Oppenheim, director of infection prevention and control, Sandwell and West Birmingham Hospitals NHS Trust.

What is MRSA?
MRSA is the commonly used abbreviation for meticillin-resistant Staphylococcus aureus, a type of S aureus that is resistant to almost all beta-lactam antibiotics, such as penicillin, flucloxacillin and cephalosporins.

In addition, some strains are resistant to other classes of antibiotics such as the macrolides (erythromycin) and fluoroquinolones (ciprofloxacin). This means there are fewer antibiotics available to treat infections caused by these strains, especially when using oral agents.


Cutaneous abcess caused by MRSA. Photograph: Public Health Image Library

Are there different types of MRSA?
It is becoming clear that there are various types of MRSA, causing different types of infection in different population groups.

The best-known strains are healthcare-associated MRSA (HA-MRSA). These are typically found in patients who have spent significant time in the healthcare system, including hospitals and nursing and residential homes.

Recently, another type has been described, known as community-acquired MRSA (CA-MRSA). These strains typically affect younger people, causing a variety of skin and soft tissue infections – sportspeople and schoolchildren have often been affected. Some of these strains produce a toxin called Panton-Valentine leukocidin and have been associated with severe infections, including a necrotising form of pneumonia.

How common is MRSA?
About one-third of people carry sensitive S aureus. Carriage of MRSA is much less common, varying from 2–10 per cent in different surveys, but occurs predominantly in individuals who have been in contact with the healthcare system.

What is the difference between carriage and infection?
The majority of individuals who have MRSA merely carry it with no adverse effects to themselves. Common sites of carriage include the nose, skin (especially the axillae and groin), throat and, in some cases, the GI tract.

Infections usually occur when an invasive procedure is performed, such as surgery or the insertion of a peripheral, central venous or urinary catheter. A variety of infections can ensue, including surgical wound infections, skin and soft tissue infections or, of most concern, a bloodstream infection that may disseminate and result in infective endocarditis, or bone or joint infections.

What is being done to reduce the incidence of MRSA?
The government has embarked on a programme to screen all patients who are admitted for routine operations or as emergencies for carriage of MRSA. The aim is to identify the majority of people carrying MRSA so they can be treated, to prevent them from developing an infection and also from transmitting the bacteria to others within the healthcare system.

What treatment is available for MRSA carriage?
The mainstay of management is decolonisation therapy, which consists of a nasal ointment, usually mupirocin, together with antiseptic body washes using chlorhexidine, triclosan or other antiseptic agents. While these may not entirely eradicate MRSA carriage, they are very effective at reducing the bioburden of the organism, so the patient is less likely to become infected or to spread MRSA.

If the patient is to undergo surgery requiring antibiotic prophylaxis, they will normally receive a glycopeptide, either vancomycin or teicoplanin, as part of their prophylactic regimen.

What treatments are available for MRSA infection?
Although there is less choice for treating MRSA infection than for sensitive S aureus, there is still a number of agents available. Treatment options for serious infections include glycopeptides, particularly vancomycin. There is now a number of newer agents available including linezolid, daptomycin and tigecycline.

In addition, a number of conventional agents such as doxycycline, trimethoprim and gentamicin are still active against some MRSA strains. However, before considering using these it is important to check the susceptibility of the particular MRSA strain in the laboratory.

What can I do to prevent the spread of MRSA?
Identifying patients who are carrying MRSA and providing a course of decolonisation therapy is the mainstay of management. Within hospitals, patients may be managed in single rooms or combined with other patients who are carriers.

In the community setting, it is necessary to take a far more pragmatic approach and implement excellent standards of hygiene for all patients. This includes careful attention to hand hygiene, use of personal protective equipment, such as gloves and aprons, when performing procedures that may contaminate the operator, and meticulous environmental cleaning.

Learning points
  • MRSA remains a concern with the public and healthcare professionals because of transmissibility and limited options for treatment of infections.
  • Identification of carriers and treatment with decolonisation therapy regimens is an important part of the current strategy to reduce MRSA transmission.
  • In the community setting, a pragmatic approach to universal improvements in hand hygiene and cleaning of the environment will help to reduce MRSA as well as other healthcare-associated infections.

Resources

  • Coia JE, Duckworth GJ, Edwards DI, et al. Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus in healthcare facilities. J Hosp Infect 2006;63 Suppl1:s1-44.
  • Working party of the British Society for Antimicrobial Chemotherapy and the Hospital Infection Society. Guidelines on the control of methicillin-resistant Staphylococcus aureus in the community. J Hosp Infect 1995;31:1-12.
  • Health Protection Agency. Guidance on the diagnosis and management of PVL-associated Staphylococcus aureus infections in England. London: HPA; 2008. Available from: .

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