MRSA stands for methicillin-resistant Staphylococcus aureus. MRSA has developed in hospitals in response to the use of drugs there. When anti biotics are used, certain bacteria may survive- those which have the necessary genes or alleles (depending on the antibiotic) to resist it. The resistant pathogens then have less competition, and can multiply their population rapidly up to the original levels, and most of the new bacteria will also be resistant to the drugs. Some will even become more resistant.

Penicillin, the first discovered antibiotic, was first introduced clinically during WWII- then 90% of the strains were sensitive to the drug, so this was usually successful. Resistent strains soon started to emerge; within about 5 years halfof all strains had become resistant, and today this proportion has reached 90%.

The issues with penicillin resistance were initially overcome by finding how penicillin worked and then making varient forms which performed a similar task, and would not be broken down by the same enzymes in the bacteria; the drugs created included methicillin, flucloxacillin, ampicillin and amoxillin, which are still used today. However, some strains have become resistant to these today, and now form MRSA.

The normal varient, Staphylococcus aureus can be found in the nose and on the skin of roughly 30% of people, and is fairly harmless, as long as it does not manage to get into abrasions, cuts, or other wounds. Even if they do infect, symptoms tend to be relatively mild, such as forming pimples or possibly conjunctivitis in the eye. More extreme reactions can occur, especially when the normal varient can enter into skin, bone, muscle, blood or the urinary tract.


For non-methicillin-resisant Staphylococcus aureus, if a cut or abrasion is infected, it may cause:

  • Pimples
  • Boils

An eye infection can lead to conjunctivitis.

More severe versions can cause pneumonia and heart disease, and can be fatal.

MRSA can also cause skin ulcers.


MRSA is rare among the general public, and is typically only found in hospitals. It is very capable of surviving away from the human body on dry surfaces, meaning it can easily be picked up by touching a contaminated surface, and visitors should regularly be washing their hands.

Up to 9% of patients in hospital may have MRSA. This is largely due to being in a confined environment, which leads to the disease spreading easily between those present. Patients may be on treatments that reduce the sensitivity of their immune systems, or have other illnesses which pose this symptom.


Probably 30% of hospital infections could be avoided by closer adherence to hygiene rules. However, many factors which cause infection are just due to being in a hospital environment, not cleanliness.

Sufferers of MRSA often have to have a long stay in the hospital, while the bacteria are removed using vancomycin and other antibiotics.


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