10.2.1

Antibiotics

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Antibiotics

Antibiotics, such as penicillin, are drugs developed to cure infections caused by bacteria. Some antibiotics work by destroying the cell wall of the bacteria so that they can't replicate.

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Antibiotics in the mid-20th century

  • Penicillin was discovered in 1928 by Alexander Fleming. This finding was amongst the most significant scientific achievements in recent history.
  • Following Fleming's discovery, penicillin became widely tested and developed by drug companies.
  • Once penicillin had proven itself as an incredibly powerful drug, the race was on to create many more antibiotic variations.
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Antibiotics don't affect viruses

  • Antibiotics do NOT destroy viruses because viruses stay inside host cells and are not living cells.
  • Antibiotics kill bacteria by specifically targeting bacterial structures & processes.
    • For example, penicillin prevents bacteria from building their cell wall. This can cause the cell to burst.
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Antibiotics are specific

  • Specific antibiotics are prescribed by medical doctors for specific diseases.
  • The use of antibiotics has greatly reduced the number of deaths from infectious bacterial diseases.

Antibiotic Resistance

Some strains of bacteria are resistant to certain antibiotics. This means that these antibiotics cannot kill them.

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Becoming resistant

  • Within a population of bacteria, some will have random mutations (random change in DNA).
    • The mutated bacteria are resistant to antibiotics and so they are able to survive, whilst the non-resistant bacteria die.
  • The resistant bacteria can reproduce rapidly because their competition (the non-resistant bacteria) has been destroyed by the antibiotic.
  • When the resistant bacteria reproduce, they produce genetically-identical copies. These copies will all be resistant to the antibiotics.
  • This is an example of natural selection.
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MRSA

  • MRSA stands for methicillin-resistant Staphylococcus aureus.
  • MRSA is often called a “superbug” because it is resistant to many antibiotics.
  • The people most commonly affected by MRSA are hospital patients.
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Clostridium difficile

  • Symptoms of C. difficile infections are largely centred around bowel irritation.
  • Recent courses of broad-spectrum antibiotics will increase someone's risk of being affected by this bacterium.
  • In 2005, a strain developed that was expressing resistance to several antibiotics. This led to several serious outbreaks across the US.
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How to stop antibiotic resistance?

  • To help prevent strains of resistant bacteria from developing:
    • Doctors should only prescribe antibiotics if they are needed and not for minor infections or viral infections.
    • Patients should complete their course of antibiotics to ensure all bacteria are killed.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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