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Lesson · Grade 8 · Science

Antibiotic resistance: how superbugs evolve

  • Grade 8
  • Science
  • 1 min 37 s
  • British Columbia
  • BC8-SC-18

Three views of one infection show a population of bacteria where a few have a random mutation that makes them resistant: the first antibiotic dose kills the rest, the 3 survivors divide about every 20 minutes into 24 in one hour, and the next dose fails because they are now superbugs. The video names this natural selection, makes clear that the bacteria become resistant (not the person), and shows that using antibiotics when they are not needed, in people or farm animals, speeds it up.

Concept: Antibiotic resistance: how bacteria evolve to survive antibiotics

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In one sentence

The question this lesson answers

Antibiotics are medicines that kill bacteria or stop them growing.

But some bacteria, called superbugs, are no longer killed by the usual antibiotics. How do they evolve?

Transcript

What the lesson says

Antibiotics are medicines that kill bacteria or stop them growing.

But some bacteria, called superbugs, are no longer killed by the usual antibiotics. How do they evolve?

Here is an infection: a population of bacteria, which means a group of the same kind living together.

By chance, a few of them already have a mutation, a random change in their DNA.

This mutation makes them resistant, which means a particular antibiotic cannot kill them.

The person with the infection takes that antibiotic. The first dose kills the bacteria that are not resistant.

Only the 3 resistant bacteria survive.

The survivors multiply. Some bacteria can divide in two about every 20 minutes.

In one hour, the 3 survivors can become 6, then 12, then 24.

So the next dose of the same antibiotic fails: all 24 are resistant superbugs.

This is natural selection: the bacteria best suited to their surroundings survive, multiply and pass on their resistance.

Be careful: the person does not become resistant. The bacteria do.

Using antibiotics when they are not needed, in people or in farm animals, speeds this up.

So antibiotics kill the bacteria that are not resistant, and the resistant ones multiply and take over.

Curriculum

Where this fits

British Columbia, Grade 8

Science, Biology: the relationship of micro-organisms with living things: vaccination and antibioticsBC8-SC-18

Previous: Antibiotics kill bacteria, not virusesNext: Epidemics and pandemics: how far a disease spreads

British Columbia, Grade 11

Life Sciences 11, Evolution and genetics: microevolution: adaptation to changing environmentsBC11-SC-152

Previous: Adaptations Are Inherited, Not Earned in a LifetimeNext: Mutations: DNA Changes That Help, Harm or Do Nothing

British Columbia, Grade 11

Science For Citizens 11, Health: personal and public health practices, including First Peoples traditional health and healing practicesBC11-SC-260

Previous: Community immunity: how vaccination stops a disease spreadingNext: Antibiotics kill bacteria, not viruses

This lesson is also listed in Grade 11.

The outcomes and strands follow the British Columbia curriculum.

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