Drug:
- Drugs are substances taken into the body that modify or affect the chemical reactions in the body.

Purpose of taking an antibiotic:
- Antibiotics are consumed for the treatment of bacterial infections.

Mode of action of antibiotics:
- Some antibiotics disrupt the cell wall of bacteria.
  - This prevents the bacteria from reproducing.
  - Sometimes the disruption of the cell wall even causes them to burst open.
- On the other hand, some antibiotics interfere with protein synthesis.
  - This ceases the growth of bacterial cells.

Why don’t antibiotics damage human cells?
- Human cells do not have cell walls.
- Likewise, the cellular structures of human cells involved in protein production are different from those of bacteria.
- Thus, antibiotics do not damage human cells as there is no target for antibiotics.
Antibiotic resistance:
- Incomplete antibiotic courses might leave some bacteria alive.
  - These bacteria will then develop a resistance to the antibiotic.
  - This means that antibiotic may have reduced, or no effect against the bacteria.
  - This trait of antibiotic resistance will then be passed down to future generations, making them all resistant.
  - This is especially dangerous in hospitals.
  - As antibiotics will be ineffective against the bacteria, the treatment choices get severely limited, which can cause further problems.
- A bacterium can develop resistance to multiple antibiotics, making them extremely dangerous.
  - M.R.S.A., short for methicillin-resistant Staphylococcus aureus, is one such example.
  - Methicillin is a type of antibiotic that disrupts the cell wall of a certain type of bacteria. Without their cell wall, bacteria cannot survive and will die.
  - S. aureus is generally a harmless bacterium commonly found on our skin.
  - However, this bacterium can pose problems for people with a weak immune system or when it enters an open wound.
  - Methicillin-resistant S. aureus cannot be treated using methicillin.

Ineffectiveness of antibiotics against viruses:
- Antibiotics kill bacteria but do not affect viruses.
- The structure of viruses is completely different from bacteria.
- Antibiotics generally target the formation of cell walls or protein synthesis.
- Viruses do not have cell walls.
- Instead, viruses invade and make use of the host cell machinery to replicate.
- Thus, antibiotics are unable to target the virus and are ineffective against them.

Measures to limit the development of antibiotic resistant bacteria:
- We should complete the course of antibiotics as prescribed by the doctor.
- We can avoid the use of antibiotics if the illness is mild and without a doctor’s prescription.
- We should reduce unnecessary usage to prevent the development of antibiotic resistance.
  - Limiting the use of antibiotics means limiting the exposure of antibiotics to bacteria.
  - If bacteria are exposed to antibiotics less frequently, the selection for antibiotic resistant bacteria will be lower.
  - In such cases, the bacteria will face other selection pressures like unfavourable environmental conditions and competition for nutrients.
  - Thus, the likelihood of survival of antibiotic resistant bacteria will decrease.
- If we use antibiotics more frequently, the selection for antibiotic resistant bacteria will occur more.
  - So, it is wise to use antibiotics only when it is essential as per doctor’s prescription.

15.01 - Drugs

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