Resistant bacteria (AQA GCSE Biology Combined Science): Revision Notes
Resistant bacteria
How resistant bacteria develop
Bacteria can become resistant to antibiotics through a process called natural selection. This happens when bacteria are exposed to antibiotics over time.
Understanding how antibiotic resistance develops is crucial for recognising why responsible antibiotic use matters. The process follows the basic principles of evolution and natural selection.
Here's how it works:
- When bacteria reproduce, mutations can occur that create new strains
- Some of these new strains might be resistant to antibiotics
- When an antibiotic is used, it creates environmental pressure
- Non-resistant bacteria are killed by the antibiotic
- Resistant bacteria survive and continue to reproduce
- Over time, the population of resistant bacteria increases
This process shows natural selection in action - the bacteria best suited to survive in the antibiotic environment are the ones that reproduce successfully.
Multiple antibiotic resistance
Some bacteria can develop resistance to more than one antibiotic. This happens because:
- Bacteria reproduce very quickly, giving them many chances to mutate
- A strain that's already resistant to one antibiotic may develop mutations that make it resistant to a second antibiotic
- These double-resistant bacteria can survive treatment with both antibiotics
- The population of these super-resistant strains then increases
This creates a serious problem because doctors have fewer treatment options available, making infections potentially life-threatening.
MRSA - a dangerous example
MRSA stands for meticillin-resistant Staphylococcus aureus. This is a particularly dangerous type of resistant bacteria.
MRSA: A Critical Healthcare Threat
Key facts about MRSA:
- S. aureus is a common bacterium that causes skin infections, respiratory problems and food poisoning
- Meticillin was the antibiotic normally used to treat S. aureus infections
- MRSA bacteria are not affected by meticillin, making infections much harder to treat
MRSA is especially problematic in hospitals because:
- Patients may have weak immune systems due to illness
- Doctors, nurses and visitors can spread the bacteria between patients
- People with wounds are particularly vulnerable to infection
Reducing antibiotic resistance
We need to slow down the development of resistant bacteria because:
- People may not be immune to these new strains
- There may be no effective treatments available
Three main strategies can help reduce antibiotic resistance:
Strategy 1: Responsible Prescribing
- Doctors should not prescribe antibiotics for viral infections or minor bacterial infections
- Antibiotics only work against bacteria, not viruses
Strategy 2: Complete Treatment Courses
- Patients must finish their entire course of antibiotics
- This ensures all bacteria are killed, leaving none to form resistant strains
Strategy 3: Limit Agricultural Use
- The use of antibiotics in farming should be restricted
- Antibiotics are often used on farms to prevent infections and increase growth rates
Good hygiene practices can also help reduce the spread of resistant bacteria.
Why new antibiotics can't keep up
The challenge of developing new antibiotics is a race against time, as bacteria evolve resistance faster than we can create new treatments.
Developing new antibiotics faces two major challenges:
- It's very expensive to create new medicines
- The development process takes a very long time
Meanwhile, bacteria continue to evolve resistance quickly, making it a race that's hard to win.
Key Points to Remember:
- Antibiotic resistance develops through natural selection - resistant bacteria survive and reproduce when antibiotics kill non-resistant ones
- Multiple resistance can develop when bacteria mutate to resist several different antibiotics
- MRSA is a dangerous example of antibiotic-resistant bacteria that causes serious hospital infections
- Responsible use of antibiotics by doctors, patients and farmers can help slow down resistance
- Complete antibiotic courses and good hygiene are essential to prevent resistant bacteria spreading