6.3.7: Resistant bacteria
Not started yet — this one needs some love.
Antibiotic-resistant bacteria arise by natural selection.
Bacteria reproduce very quickly, so they can evolve rapidly.
A random mutation can make a bacterium resistant to an antibiotic.
When the antibiotic is used, non-resistant bacteria are killed, but the resistant bacteria survive and reproduce.
The resistant strain spreads because people are not immune to it and there is no effective treatment.
MRSA is an example of a bacterium resistant to antibiotics.
To slow down the development of resistant strains:
doctors should not over-prescribe antibiotics (e.g. not for viral or non-serious infections)
patients should finish the whole course so all bacteria are killed and none survive to mutate
the agricultural use of antibiotics should be restricted.
Developing new antibiotics is slow and costly, so it is hard to keep up with new resistant strains.
Common exam mistakes
Resistance arises by random mutation then natural selection — bacteria do not "want", "try" or "decide" to become resistant.
The antibiotic does not cause the mutation; it selects for bacteria that are already resistant.
Say resistant bacteria survive and reproduce, passing on the resistance — not that they "get used to" the antibiotic.
Antibiotics kill bacteria, not viruses; taking them for a cold or flu does nothing and adds to resistance.
"Finish the course" matters because stopping early leaves surviving bacteria that can multiply into resistant strains.
Use MRSA as the named example if asked.