Methicillin-resistant Staphylococcus aureus

From Academic Kids

Methicillin-resistant Staphylococcus aureus, (MRSA) is a specific strain of the Staphylococcus aureus bacterium that has developed antibiotic resistance, first to penicillin since 1947, and later to methicillin and related anti-staphylococcal drugs (such as flucloxacillin). Popularly termed a "superbug", it was first discovered in Britain in 1961 and is now widespread. Non-methicillin resistant Staphylococcus aureus is termed methicillin-susceptible Staphylococcus aureus (MSSA) to make the distinction.

While an MRSA colonisation in an otherwise healthy individual is not usually a serious matter, infection with the organism can be life-threatening to patients with deep wounds, intravenous catheters or other foreign-body instrumentation, or as a secondary infection in patients with compromised immune systems. Part of the problem is that MRSA does not respond to the antibiotics normally prescribed for the infections in question, and can hence progress unchecked.

Because cystic fibrosis patients are often treated with multiple antibiotics in hospital settings, they are often colonised with MRSA, potentially increasing the rate of life-threatening MRSA pneumonias among them. The risk of cross-colonisation has led to increased use of isolation protocols among these patients.

In the US there are increasing reports of outbreaks of MRSA colonisation and infection through skin contact in locker rooms and gymnasiums, even among healthy populations. MRSA causes as many as 20% of Staphylococcus aureus infections in populations that use intravenous drugs. These out-of-hospital strains of MRSA, now designated as community-acquired, methicillin-resistant staph. aureus, or CAMRSA, are not only difficult to treat but are especially virulent. CAMRSA apparently did not evolve de novo in the community, but represents a hybrid between MRSA which escaped from the hospital environment and the once easily treatable community organisms. Most of the hybrid strains also acquired a virulence factor which makes their infections invade more aggressively, resulting in deep tissue infections following minor scrapes and cuts, and many cases of fatal pneumonia as well.

As of early 2005, the number of deaths in the United Kingdom attributed to MRSA has been estimated by various sources to lie in the area of 800 to 955 per year.

Vancomycin and teicoplanin (glycopeptide antibiotics) are used to treat MRSA infections. These drugs are administered intravenously. Several new strains of the bacterium have been found showing antibiotic resistance even to vancomycin and teicoplanin; those new evolutions of the MRSA bateria are dubbed "vancomycin intermediate-resistant Staphylococcus aureus" (VISA). Linezolid and quinupristin/dalfopristin are more recent addition to the therapeutic arsenal, generally reserved for severe infections which do not respond to glycopeptides.


At the end of August 2004, after a successful pilot scheme to tackle MRSA, the British National Health Service announced its Clean Your Hands campaign. Wards will be required to ensure that alcohol-based hand rubs are placed near to all beds so that staff can hand wash more regularly. It is thought that if this cuts infection by just 1% the scheme will pay for itself many times over. [1] (

See also

External links and references

es:Staphylococcus aureus resistente a meticilina nl:Methicilline-resistente staphylococcus aureus ja:MRSA fi:MRSA


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