Resistant Bacteria (AQA GCSE Biology: Combined Science)

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Mutations & Bacterial Evolution

  • The theory of evolution by natural selection is now widely accepted and many sources of data are now available to support the theory of evolution
  • One very clear piece of evidence for evolution is antibiotic resistance in bacteria
  • An antibiotic is a chemical that can kill or inhibit the growth and reproduction of bacteria
  • Antibiotics are extremely useful to humans as some bacteria are pathogenic and can cause life-threatening disease
  • Bacteria reproduce, on average, every 20 minutes and therefore evolution occurs in a much shorter time span
  • Like all other organisms, within a population, there will be variation caused by mutations
  • A chance mutation might cause some bacteria to become resistant to an antibiotic (eg penicillin)
  • When the population is treated with this antibiotic, the resistant bacteria do not die
  • This means they can continue to reproduce with less competition from non-resistant bacteria, which are now dead
  • Therefore the genes for antibiotic resistance are passed on with a much greater frequency to the next generation
  • Over time the whole population of bacteria becomes antibiotic-resistant because the bacteria are best suited to their environment

Antibiotic_resistance, IGCSE & GCSE Biology revision notes

Development of antibiotic resistance in bacteria

 

  • This is an example of natural selection that humans have helped to develop due to overuse of antibiotics in situations where they were not really necessary, for example:
    • For the treatment of non-serious infections
    • Routine treatment to animals in agriculture
    • Failure to finish the prescribed course of antibiotics

MRSA

  • Increases in the population of antibiotic-resistant bacteria cause infections and diseases which are harder to control as it is difficult to find antibiotics that certain strains of bacteria are not resistant to
  • An example of this is MRSA, a very dangerous bacterial strain that is resistant to most antibiotics
  • If someone gets infected with MRSA they cannot be treated easily

Antibiotic Development

  • The increase we are currently seeing in antibiotic resistance is encouraging drug companies to develop new antibiotics that are effective against these new resistant strains, such as MRSA
  • However, the number of new antibiotics discovered has slowed significantly
  • Developing new antibiotics is also a very costly process
  • Some scientists are worried we may not be able to keep up with the demand for new antibiotics, as more and more antibiotic-resistant strains evolve

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Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.