Syllabus Edition

First teaching 2023

First exams 2025

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Antibiotic Resistance (HL IB Biology)

Revision Note

Ruth

Author

Ruth

Expertise

Biology

Antibiotic Resistance

  • Within a bacterial population, there is variation caused by mutations (as occurs in populations of all species)
  • A chance mutation might cause some bacteria to become resistant to an antibiotic (e.g. penicillin)
  • When the population is treated with this antibiotic, the resistant bacteria do not die
  • This means the resistant bacteria can continue to reproduce with less competition from the 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
    • As bacteria only have one copy of each gene, a mutant gene will have an immediate effect on any bacterium possessing it
  • Over time, the whole population of bacteria becomes antibiotic-resistant because the antibiotic-resistant bacteria are best suited to their environment
  • This is an example of evolution by natural selection
  • Some pathogenic bacteria have become resistant to penicillin as they have acquired genes that code for the production of the enzyme β-lactamase (also known as penicillinase), which breaks down penicillin

Antibiotic resistance diagram

Antibiotic_resistance, IGCSE & GCSE Biology revision notes

Bacteria evolve rapidly as they reproduce and acquire random mutations, some of which confer resistance

The future of antibiotic resistance

  • Antibiotic-resistant strains are a major problem in human medicine
  • New resistant strains are constantly emerging due to the overuse of antibiotics
    • By using antibiotics frequently, humans exert a selective pressure on the bacteria, which supports the evolution of antibiotic resistance
  • Scientists are trying hard to find new antibiotics that bacteria have not yet been exposed to, but this process is expensive and time-consuming
  • Some strains of bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), can be resistant to multiple antibiotics and they create infections and diseases which are very difficult to treat
  • When antibiotics were discovered, scientists thought they would be able to eradicate bacterial infections, but less than a century later a future is being imagined where many bacterial infections cannot be treated with current medicines

Measures to avoid antibiotic resistance

  • Antibiotic resistance in bacteria is an example of natural selection that humans have helped to develop through incorrect use or overuse of antibiotics
  • Implementation of certain measures can help to avoid antibiotic resistance. These measures may include:
    • Avoiding prescription of antibiotics for non-serious or non-bacterial infections
    • Maintaining high standards of hygiene in the hospital environment
    • Minimising use of antibiotics for routine treatment of animals in agriculture
    • Development of new types of antibiotic

NOS: The development of new techniques can lead to new avenues of research

  • The rise of antibiotic resistance presents significant challenges within the medical field, as it renders the treatment of specific illnesses more challenging and contributes to higher mortality rates
  • Addressing antibiotic resistance stands as a top priority for the World Health Organization (WHO)
  • The future effectiveness in treating common infections and minor injuries hinges upon the development of novel antibiotics
  • Presently, researchers are making use of chemical libraries to craft and produce fresh antibiotics
  • Within these screening libraries, there exists a wealth of information about numerous chemical compounds possessing antibacterial characteristics
  • Innovative methodologies like incorporating chemical libraries introduce promising avenues for countering the issue of antibiotic resistance

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