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Staphylococcus
aureus:
Staphylococcus aureus is a gram positive bacterium commonly found on the skin and in the nose of between 30 – 50 % of healthy people and can be responsible for infections at many sites in the body. It is well know for its role in hospital-acquired (nosocomial) infections and is particularly versatile with regard to survival in the hospital environment. It is a problem endemic in many hospitals throughout the world which can sometimes reach epidemic proportions. Methicillin Resistant Staphylococcus aureus (MRSA): Penicillins were introduced in the 1940’s for the treatment of Staphylococcal infections. Within a period of only a few years many strains of Staphylococcus aureus had developed resistance to penicillin. This was due to the production by the bacteria of an enzyme, ß-lactamase, which inactivates penicillin. Introduction in 1959 of semi-synthetic ß-lactam penicillins such as methicillin, was thought to be the answer to this problem. However, within two years of its introduction, the first isolate of methicillin resistant Staphylococcus aureus (MRSA) was reported (Jevons 1961). This new resistance is due to an altered penicillin-binding protein (PBP 2a). Resistance to methicillin implies resistance to all semi-synthetic penicillins and to other ß-lactam antibiotics including the cephalosporins. Resistance to other antibiotics, for example gentamycin, has also been acquired over the years by strains of MRSA. Treatment of resistant infections now depends on potentially toxic and expensive antibiotics such as glycopeptides for example vancomycin. Gentamycin Methicillin Resistant Staphylococcus aureus (GMRSA): MRSA that is also resistant to Gentamycin. Vancomycin Resistant enterococci (VRE): A strain of enterococci showing resistance to vancomycin. ————————————————————————————————————
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