Evidence of Evolution: Resistant Bacteria

Antibiotic Resistance

Learning Goals:

  • Explain how bacteria become resistant to antibiotics.

  • Describe ways to reduce the development of resistant bacteria.

1. Rapid Evolution in Bacteria

  • Bacteria reproduce very quickly (as fast as every 30 minutes), allowing them to evolve rapidly.

  • In the 1940s, antibiotics like penicillin began treating bacterial infections.

  • Over time, some bacterial strains have evolved to resist antibiotics (e.g., MRSA).

2. How Antibiotic Resistance Develops

  1. Genetic variation exists in bacterial populations due to mutations.

  2. A mutation may make a bacterium resistant to a particular antibiotic.

  3. Antibiotic treatment kills non-resistant bacteria, leaving the resistant bacterium to survive.

  4. The resistant bacterium reproduces rapidly, spreading the resistance through the population.

  5. Result: the population of resistant bacteria rises, and infections become harder to treat.

3. Reducing the Development of Resistance

  1. Avoid inappropriate use of antibiotics

    • Antibiotics should not be used for viral infections.

  2. Complete the full course of antibiotics

    • Ensures all bacteria are killed and prevents survival of resistant mutants.

  3. Restrict use in farming

    • Reduces unnecessary exposure and selection for resistance.

Challenge:

  • Developing new antibiotics is slow, expensive, and cannot keep pace with the rapid emergence of resistant strains.

✅ Key Points

  • Antibiotic resistance is an example of natural selection in action.

  • Proper use of antibiotics and limiting unnecessary exposure are crucial to slow resistance.

  • New antibiotics are needed, but prevention is the most effective strategy.