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.