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Drugs and Antibiotics

15.1 Drugs

  • Definition: A substance taken into the body that modifies and affects chemical reactions within the body, often derived from plants.
  • Functions of drugs:
    • Cure diseases and heal wounds.
    • Induce hallucinations or feelings of excitement.
    • Extend lifespan.
    • Relieve pain.

15.2 Medicinal Drugs

  • Antibiotics:
    • Substances that kill bacteria by damaging their cell walls without harming other living cells.
    • Often made from fungi, such as Penicillium sp.
    • Fungi produce antibiotics to eliminate bacteria living nearby due to competition for food.
    • The first antibiotic was penicillin, derived from the fungus Penicillium sp. found growing on decaying fruit.
    • Antibiotics are effective against bacteria but not viruses.

Antibiotic Resistance

  • Selection Pressure: The introduction of antibiotics into the body exerts selection pressure on bacteria, increasing the likelihood of resistance.
  • When a person infected with bacteria is treated with penicillin, the bacteria are unable to grow new cell walls, and they burst open.
  • The probability of individual bacteria developing resistance is low. However, due to the large population size of bacteria, resistant mutants can emerge.
  • A mutant bacterium can reproduce and form a large population of resistant bacteria.
  • The overuse of antibiotics increases selection pressure, leading to the development of resistant bacterial strains that are difficult to control.
  • Staphylococcus aureus is a bacterium that has developed resistance to multiple antibiotics, known as MRSA, causing infections that are difficult to treat.

Minimizing Antibiotic Resistance (MRSA)

  • Use antibiotics only when essential.
  • Ensure the full treatment course is completed.
  • Prescribe/use antibiotics less often.
  • Avoid antibiotics for viral or fungal infections.
  • Ensure patients complete their full course of antibiotics.
  • Develop new antibiotics.
  • Avoid using the same antibiotics for extended periods; rotate antibiotics.
  • Use combinations of antibiotics.
  • Implement isolation measures for patients with antibiotic-resistant infections.
  • Maintain good hygiene to prevent the spread of infection.

Natural Selection Example: Antibiotic Resistance in Bacteria

  • Variation exists within bacterial populations.
  • Antibiotic treatment leads to the "selection" of the fittest bacteria, i.e., those resistant to the antibiotic.
  • These surviving bacteria with advantageous characteristics reproduce, passing on their resistance to offspring.