Penicillin And Staphylococcus Aureus Biology Essay

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Prior to the discovery and subsequent wide spread use of Penicillin, countless people died because of bacterial infections, including wounded soldiers during World War II. The discovery of penicillin revolutionized medical practice and saved the lives of many soldiers. Staphylococcus Auereus, ("S. Aureus") by contrast, is a common, potentially dangerous pathogen which can cause life-threatening infections, such as endocarditis, a disease in which the valves of the heart become infected. Up to thirty percent of the population carry this potentially deadly bacteria…it lives inside their noses!

Penicillin is a group of antibiotics, which were developed from the fungi Penicillium. The British microbiologist Alexander Fleming is credited with the discovery of penicillin, during 1928. The chemical structure of penicillin is R-C9H11N2O4S where the R is the variable which changes dependent on the different type of penicillin. Penicillin is used in the treatment of a wide range of bacterial infections, such as staphylococcal infections.

S. Aureus (commonly known as golden staph) is one of over twenty species of Staphylococcus. Together with Staphylococcus epidermidis, S. Aureus are the only two types of Staphylococcus that have important interactions with human beings. S. Aureus is part of the genus Staphylococcus which is part of a bacterial group Staphylococcaceae which also includes the Salinicoccus, Macrococcus, Gamella, Genera. An individual staphylococcus cell is a perfect sphere with a diameter of one micrometer. Staphylococci grow in clusters, which look somewhat like bunches of grapes. When S. Aureus is cultured in a lab it forms a large, yellow colony of bacteria, in contrast to S. Epidermidis, which cultures a comparatively small, white colony. When cultured on blood agar, S. aureus is often haemolytic, meaning it breaks down the red blood cells. S. Aureus multiplies in temperatures between fifteen and forty five degrees Celsius, and water with concentrations of salt (sodium chloride) of up to fifteen percent.

The discovery of penicillin was in fact accidental. After travelling to France during the First World War to treat injured soldiers at the Western Front, physician and microbiologist Alexander Fleming saw that there was no cure for most bacterial infections - many soldiers were dying from infected wounds. Whilst practicing in St Marys Hospital London, Fleming studied the bacteria staphylococci, which can infect wounds. By accident, he left one petri dish open, which became contaminated with a green-blue looking mould. Fleming noticed that a ring of bacteria grew around and a short distance from the area of mould, and deduced that the mould had released a substance which had stopped the growth of the bacteria. Fleming took samples of the mould and found that it was from the penicillium notatum, accordingly he named the substance penicillin. It was not until 1941, through developments made by Australian scientist Howard Florey and German Scientist Ernst Chain that a purified form of penicillin came into medical use, revolutionising medical practice. Further advancements made by Florey and Chain resulted in the formulation of a technique of large scale production of the drug.

S. Aureus usually forms colonies on the skin and in the nose. Contact with S. Aureus alone, is not harmful. It is estimated that approximately between twenty and thirty percent of people "carry" the bacteria in their nose. However, if a S. Aureus bacterium was to enter an open wound or cut, it could cause an acute infection, such as a skin infection, or possibly a serious infection, such as Meningitis (the infection of the membranes covering the brain). S. Aureus spreads through the contact of skin with infected regions. S. Aureus infections were originally treated with penicillin.

The first widespread medical application of Penicillin was during the Second World War by US army. The use of the antibiotic severely reduced the mortality rate of injured soldiers with bacterial infections. After the war Australia became the first country to provide civilian access to the antibiotic.

S. Aureus outbreaks are major problems in hospitals. There are many people with wounds from surgery, who are therefore more susceptible to serious infections. The overuse of disinfectants can result in the mutation of the bacterium and the formation an antibiotic resistant "superbugs". During the 1970's a methicillin resistant form of the pathogen plagued hospitals worldwide, infecting many patients. These days the superbugs are even found outside hospitals, in the community.

Penicillin fights bacteria by preventing the formation of the bacterial cell wall. The drug disables an enzyme called transpetidase, which is needed for the cross linking of the cell walls, thus stopping the synthesis of the cell wall, causing the bacteria to die.

S. Aureus infections are very common, however most have minor complications and are restricted to the wound or break in the skin through which it entered the body. However, once S, Aureus enters the bloodstream, it can infect the lungs (Pneumonia), the lining of the brain (meningitis) and the veins (septic phlebitis). Entry into the bloodstream of S.Aureus can also result in Septicemia, which can be fatal. Septicemia is when the bloodstream becomes infected with a pathogen such as S.Aureus, in such quantities, that it can spread through the body quickly, and if not treated with intravenous antibiotics quickly, can result in death.

The various types of penicillin include:

Penicillin V

Penicillin G






Penicillin is a bacteriostatic antibiotic, which means it stops new bacteria from forming, as opposed to a bactericidal antibiotic, which destroys existing bacteria.

S. Aureus was treated with penicillin until an antibiotic resistant form of the bacterium developed. These antibiotic resistant strains of of the bacteria form when a course of antibiotics does kill all of the bacteria cells. The remaining bacteria cells thrive because they no longer have to contend for resources, with the rest of the colony. They then mutate to form antibiotic resistant strain of the bacteria. S. Aureus infections are now treated with the antibiotics methicillin and vancomycin.

Whilst penicillin may have been superceded by other antibiotics, it is still used to treat minor infections such as pharyngitis and ear infections. Despite the development of superbugs, penicillin has saved countless lives and its discovery was one of the most important medical advancements made during the first half of the twentieth century. S, Aureus is carried by up to 30 percent of the population without any ill effects. A S. Aureus infection is generally mild and cured by antibiotics. However, if the infection spreads into the bloodstream, consequences may be serious, for example, the patient may contract septicaemia, which can quickly kill, although most S. Aureus infections stay at the site of the wound or broken skin, and are easily treated with the right antibiotic.