How has the bacterium Staphylococcus aureus become so resistant to antibiotics such as penicillin?
2 Answers
There has been genetic drift. The bacteria that have lost genetic material have become the dominate form of Staphylococcus aureus.
Explanation:
Bacteria become resistant by losing genetic material that the antibiotics like penicillin use to attack the reproduction of the bacteria. ( The Beak of The Finch pages 260-262)
The bacteria that have lost the genetic material are best adapted to survive in an environment with the presence of antibiotics. These bacteria are able to reproduce while the normal bacteria are not able to reproduce. This causes a genetic drift where the dominate population is the bacteria that have lost the genetic material.
Penicillin has been used for so many years that the genetic drift has become so strong that the strains of the mutated are very common.
After a period of time without penicillin it is possible that the genetically stronger bacteria will repopulate and again become the dominate form of the bacteria. In the mean time it is important to find other types of antibiotics that are effective against the Staphlococcus.
First thing that comes to my mind is that, bacteria S.a. developed resistance to penicillin decades ago. Penicillin was the first antibiotic to fail spread of infections caused by S.a. and thereafter it has shown resistance to a series of antibiotics.
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Penicillin resistance in particular was achieved by action of blaZ gene. This gene codes for an enzyme named beta lactamase: the enzyme hydrolyses beta lactum ring of beta lactum antibiotics, such as Penicillin, Cephalosporin, etc.
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