Evolution of Antibiotic Resistance-Printable Format - Teach ...

Part I: Define the Problem
Activity A) Investigate Resistance to Antibiotics—Teacher’s Guide
Overview: Begin the evolution unit with a real problem: bacterial resistance to antibiotics.
Learning Objectives: Students will understand what antibiotics are and what they do (i.e.
they are chemicals that kill bacteria, which humans have co-opted and use to fight
bacterial infections); students will understand that antibiotics do not kill all of the
bacteria they are used against.
Class Time: 2 – 3 days
Day 1: Have students set up experiment on resistance.
Day 2: Have students examine their experiment and make observations; small
group/full class discussion of the significance of their findings.
Background Information: “What are Antibiotics?” and “Antibiotic Resistance”
Materials: petri dishes filled with nutrient agar (one or two for each student)
sterile cotton swabs
distilled water (or tap water, if distilled water is unavailable)
antibiotic disks (several kinds, one disk of each per student)
control disks (one per student)
markers
scotch tape (to seal the lid of the petri dish to the bottom, for transport)
copies of worksheet (one for each student)
In this exercise, students will be introduced to simple methods used in microbiology.
Students collect bacteria from the classroom or themselves, and test these bacteria against
several antibiotics. They will see “first-hand” the effects that antibiotics have on bacteria, as
well as the ability of some bacteria to resist antibiotics. This will lead into a
lecture/discussion on antibiotics, resistance to antibiotics, and the increasingly serious public
health crisis.
Materials can be obtained from a biological supply catalog. Blank control disks and
antibiotic disks are typically sold in packs of 50. I would suggest you use several different
types of antibiotics that have been very commonly used; including both antibiotics that work
on gram positive bacteria and antibiotics that work on gram negative bacteria; for example,
erythromycin, penicillin, streptomycin, and tetracycline. Tetracycline has been used a lot for
skin infections (e.g. acne), so this would be a particularly good one to use if you have
students swab the oily parts of their faces. If you do not have microbiology materials inhouse,
you can also obtain petri dishes prepared with nutrient agar from these sources.
Encourage students to collect bacteria from a variety of sources (each student choosing
one source only). Sink drains, or other moist places work well, as do places with a lot of
dust. They could even swab themselves (e.g. the oily skin around their nose or forehead).
How long it takes for visible growth of the colonies will depend on the environmental
conditions where they are stored. Ideally, place the petri dishes in an incubator set at 37 o C,