Download Antibiotics and resistance activity

Antibiotic misuse tutorial
VGEC: Teacher worksheet
Antibiotics and resistance activity
Intended learning outcomes
 To understand how antibiotics are used to treat infections
 To understand how misuse of antibiotics can lead to antibiotic
resistant infections
Materials
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A student volunteer
Two sets of differently coloured ‘Post It Notes’
Some small sweets (antibiotics)
Introduction
Bacteria and infection
Bacteria are a domain of prokaryotic microorganisms. Many bacteria can live in our bodies
(I.E gut, mouth etc) without causing any damage, and may even form a mutually beneficial
relationship (commensals). Some bacteria however, if they are able to colonise the relevant
part of the body can result in infections, we refer to these as pathogens. These infections
can often go on to cause dangerous diseases such as meningitis, severe food poisoning and
septicaemia (blood poisoning).
Antibiotics and resistance
Antibiotics are drugs used to treat infections caused by bacteria. They work by inhibiting a
key process in a bacterium’s biology (for example protein synthesis). Since the discovery of
penicillin, we have been able to treat the vast majority of bacterial infections with relative
ease. However we are now faced by infectious bacteria that have evolved resistance to
nearly all of our clinical antibiotics. *Note: mutations leading to resistant bacteria are always
occurring; it is our misuse of the drugs that have allowed resistant bacteria to flourish.
Antibiotic misuse tutorial
Antibiotic misuse
When a population of bacteria contains a few cells that are resistant to antibiotics, they are
often outcompeted by the majority of the susceptible population. In cases where we have
misused antibiotics, the susceptible cells are killed by the drug, allowing the resistant cells to
grow and dominate the population. Examples of antibiotic misuse include:
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Not completing a course of antibiotics – antibiotic courses have been tested for
conditions to best treat bacterial infections
Using antibiotics to treat non-bacterial infections – Most prescribed antibiotics
are targeted against bacteria (however viral antibiotics do exist), using these drugs to
treat viral infections selects for resistant bacteria in the body which can on to cause
drug resistant infections in the future
The Activity
Take your volunteer and at the front of the class stick a dozen or so ‘Post It Notes’ (e.g. blue)
on to his/her front jacket/pullover and 3 of a different colour (e.g. red).
Tell the students and emphasise that this represents a normal and harmless bacterial
population living on or inside of any individual, the red ones represent the small number of
more antibiotic resistant bacteria that will be present in any bacterial population. This is a
result of the constant mutation and variation occurring in all bacteria.
1.) To demonstrate the unfinished course problem:
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Volunteer student pretends to be ill with a bacterial infection, give him an AB (sweet),
and take a few blue notes off for day 1.
Another AB for the next day, take a few more blues off.
Another AB for day 3 and remove all the blue notes, volunteer feels well and stops
the 5 day AB course.
Ask students what will happen to the resistant population now there is no
competition; slap loads of the red ones on.
You could remove one or two of the red ones to show that they are killed as well but
need the full AB course to eliminate them. Leave at least one red one.
2.) To demonstrate the inappropriate use problem:
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Student starts ‘plastered’ as with first activity.
Tell the pupils the volunteer has a viral infection but does not realise AB’s do not kill
viruses.
Give him an AB or ABs (sweet/s) and take off some notes, students see the red
population is unaffected or slightly so, but the normal healthy population is being
wiped out. This again allows the red (resistant) population to explode because of the
reduced competition. Slap on loads of red ones.
Antibiotic misuse tutorial
The Student Worksheet
You should now hand out the attached student worksheet, which aims to
reinforce the concepts delivered through the above activity.
Students should describe what the storyboard shows, using the concept of intra-community
competition in their answers. By year 10, students should have covered mutation, and as
such should seek to answer the questions using genetic principles.
Example Answers
Patient 1
1.) In normal bacterial population, mutation in the
Normal bacterial
population
absence of selective pressure is constantly
ongoing. It is therefore likely that resisent cells will
be present in a population.
Antibiotic taken for viral
infection – end of course
2.) Taking antibiotics when they are not required kills
of the otherwise harmless susceptible bacteria in a
population.
Resistant
cells grow
3.) This allows the remaining resistant cells to
proliferate. If these cells go on to cause infection,
they will be far more difficult to treat.
Patient 2
Normal bacterial
population
1.) Some of the susceptible bacteria will be killed
1st day of course
2.) More bacteria are killed by the anitibiotic
2nd day of course
3.) Stopping the course early leaves some reistent
3rd day of course
cells, some cells can even had resistance
- Course stopped
inducted by sub-lethal exposure.
4.) Later on, the resistant cells will dominate,
7 days after
stopping course
causing another infection. This population
however (unlike the original), will not respond to
therapy.