M.R.S.A Glog

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by BradyHillier
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Evolutionary Biology

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M.R.S.A Glog

M.R.S.AEvolution of a Super Bug

For hundreds of years humans have been developing effective antibiotics to eliminate the seriously harmful Staphylococus Aureus infection.

Natural Selection is the process whereby organisms better adapted to their enivronment survive and produce more offspring. Those organisms that do not survive can not produce more offspring, not allowing for the passing of their 'inferior' genes. Through natural selection the most well adapted organism survive, this allows for their offspring to inherit the advantageous traits. Selection agents are the environmental pressures that make natural selection possible. Selection agents include predators, competition and climate change. These selection agents eliminate those of the species, who cannot survive as effectively as the other well adapted organisms. Mutations in genes of organisms can create either positive, negative or neutral traits that can assist the organism to survive. These mutations can lead to new advatageous traits being passed down to offspring. Over long periods of time natural selection can lead to the evolution of a species. This occurs when organisms are seperated, natural selection can change the traits of these two organisms creating new sub species. Aventually this can lead to the evolution of new species who can no longer produce fertile offspring together.

In 1959 Methicillin (a strong antibiotic) was licensed and first used to eliminate the seriously harmful Penicilin Resistant Staphylococus Aureus. Only two years later, the first reports of Methicilin Resistant Staphylococus Aureus or M.R.S.A was first discovered. The evolution of a normal species averagely takes centuries to occur. Although, due to bacteria's ability to transfer plasmids, copy DNA and multiply in a rapid rate, the possibility of a super bug has occured. M.R.S.A is still rapidly increasing, evloving and being fed by humans attempts to solve the epidemic problem. Since the first Staphylococus Aureus Infection, the super bug has not yet evolved, but changed strains. Over 359 strains of M.R.S.A have been identified around the world. Eleven majorly cloned strains have been discovered and are slowly evolving to become resistant to the strongest antibiotics know of, including Vancomycin.

The Evolution of M.R.S.A is a phyletic evolution as the organism is evloving down the same path by itself without changing and evolving into different species. M.R.S.A does this effectively and quickly especially through the use of bacteria's ability to rapidly produce offspring. M.R.S.A strains can also copy over DNA between two cells through the process of trading plasmids. This allows for the organism to aquire the antibiotic resistant genes from other strains of the infection.

M.R.S.A effectively evolved new strains over a course of time well under a century. This was only possible due to the pocess through how fast bacteria can transfer and produce new offspring allowing the passing down of advantageous traits. Staphylocucs Infections strains of the virus only took a few years to adapt resistance against less effective antibiotic such as penicilin. Where M.R.S.A will need a longer period of time to adapt to the strong antibiotic Vancomycin as it is nearly 99% effective against recent M.R.S.A strains. Although evidence has already been obtained showing the recent adaptation of Vancomycin resistant strains. This was experimented on through a patient over a six month period, where the patient was constantly exposed to M.R.S.A and Vancomycin. The M.R.S.A infection began the adaptation of the antibiotic Vancomycin.

Each strain of the M.R.S.A virus all vary in their effectiveness at the resistance of antibiotics. Previous strains of Penicilin Resistant Staphylococus Aureus have been less effective against antibiotcs which led to the evolution of the more resistant M.R.S.A. The more effective strains of the infection commonly inherit resistance to different antibiotics. They then spread and trade their resistance to other strains causing the mass evolution of a super bug.

Variation is found in every strain of the infection. The ability of bacteria to reproduce quickly allows for selective advategous to be carried on to offspring at a constant rate much faster than other organisms. The change in chemical environments acts as the selection agent as the bacteria dies. If any bacteria survive they have inherited the gene of antibiotic resistance. This can further be spread quickly allowing for the rapid evolution of infections such as M.R.S.A.


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