Antibiotic resistance evolves when bacteria survive treatment and pass on resistance genes.
Selection Pressure
- Antibiotics kill sensitive bacteria
- Resistant mutants survive and multiply
- Resistance spreads through population
Fitness Trade-offs
- Resistance often has a fitness cost
- Without antibiotics, sensitive outcompete resistant
- With antibiotics, resistant have advantage
Implications
Overuse of antibiotics accelerates resistance. Antibiotic stewardship programs aim to reduce unnecessary use.