Resistant bacteria (AQA GCSE Biology): Revision Notes
Resistant bacteria
What are resistant strains?
Resistant strains are bacteria that can survive when antibiotics are used against them. These bacteria have developed ways to protect themselves from medicines that would normally kill them.
When bacteria reproduce, mutations can happen. Some of these mutations might make a bacterium resistant to an antibiotic. This means the antibiotic cannot kill that particular bacterium.
The development of antibiotic resistance is a natural evolutionary process. However, human activities can greatly accelerate this process, making it a serious public health concern.
How resistance spreads through populations
Resistant bacteria become more common through a predictable process driven by natural selection:
Step-by-step Process: How Resistance Spreads
- Mutations occur - Some bacteria develop resistance through genetic changes
- Selection pressure - When antibiotics are used, non-resistant bacteria die
- Resistant bacteria survive - Only the resistant ones are left alive
- Population grows - The resistant bacteria reproduce rapidly
- Resistance spreads - Soon most bacteria in the population are resistant
This process happens because bacteria reproduce very quickly and in large numbers, making mutations and selection extremely rapid.
Multiple antibiotic resistance
Some bacteria can become resistant to more than one antibiotic. This happens because:
- The presence of antibiotics creates an environment that favours resistant bacteria
- A strain resistant to one antibiotic may develop mutations that make it resistant to other antibiotics too
- These super-resistant bacteria can survive multiple different treatments
- The population of multi-resistant bacteria then increases rapidly
Multiple antibiotic resistance makes infections much harder to treat successfully and can lead to life-threatening situations where no effective treatment options remain.
MRSA - a dangerous example
MRSA stands for meticillin-resistant Staphylococcus aureus.
- S. aureus is a common bacterium that causes skin infections, chest infections and food poisoning
- Meticillin used to be the main antibiotic for treating S. aureus infections
- MRSA bacteria are resistant to meticillin, so this antibiotic doesn't work against them
Why MRSA is dangerous in hospitals
Hospital Dangers of MRSA:
MRSA causes serious problems because:
- Patients may have open wounds or weak immune systems
- Doctors, nurses and visitors can accidentally spread bacteria between patients
- Standard antibiotic treatments don't work
- Infections can become life-threatening
Reducing antibiotic resistance
We must reduce the development of resistant bacteria because:
- People may not be immune to these new strains
- There may be no effective treatments available
Three key ways to reduce resistance
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Doctors should not prescribe antibiotics for viral infections or minor bacterial infections
- Antibiotics only work against bacteria, not viruses
- Unnecessary use increases resistance
-
Patients must finish their antibiotic courses
- This kills all bacteria, leaving none to develop resistance
- Stopping early leaves some bacteria alive to mutate
-
Restrict antibiotic use in agriculture
- Farmers use antibiotics to prevent infections and increase growth rates
- This creates more opportunities for resistance to develop
Good hygiene helps too
Careful hygiene reduces the spread of resistant bacteria between people and places. Simple measures like proper handwashing can significantly impact the transmission of resistant strains.
Why developing new antibiotics is difficult
The pharmaceutical industry faces significant challenges in antibiotic development:
- It is expensive to develop new antibiotics
- The development process takes a very long time
- New antibiotics may not keep up with the appearance of new resistant strains
Key Points to Remember:
- Resistant bacteria develop through mutations and natural selection
- Multiple resistance makes bacteria much more dangerous
- MRSA is a serious example of antibiotic-resistant bacteria
- Reducing resistance requires careful antibiotic use by doctors, patients and farmers
- Good hygiene helps prevent the spread of resistant strains