Repeated Antibiotic Exposure and Bacteria Resistance
Hard
Why do antibiotics sometimes stop working? When bacteria survive a dose of antibiotic, the survivors can pass their resistance on to the next generation.
You spread E. coli bacteria on agar plates and place filter paper discs soaked in ampicillin at three concentrations: 1 mg, 3 mg, and 5 mg. After four days, you measure the inhibition zone (the clear ring around the disc where no bacteria grow). Then you collect surviving bacteria from the edge of that zone and repeat the process for five generations.
With each generation the inhibition zone shrinks. The 1 mg zone drops from 24 mm to 11.5 mm by the fifth round. Higher concentrations also shrink but more slowly.
Hypothesis
The hypothesis is that repeated use of antibiotics causes bacteria to develop resistance which in turn, causes the antibiotic to become less effective in eliminating the bacteria.
Method & Materials
You will prepare 15 Petri dishes, mix different concentrations of antibiotics, and inoculate the Petri dishes with bacteria. After 4 days, you will measure the diameter of the inhibition zone and record your results.
You will need 15 agar Petri dishes, 15 disinfected swabs, 1 bottle of disinfected water, 1 piece of filter paper, 1 hole puncher, 4 test tubes, 1 measuring cylinder, 100mg of antibiotic ampicillin, 1 digital weighing scale, 1 beaker of water, E Coil bacteria culture, 1 forceps, and 1 marker pen.
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See what’s includedResults
The results of this experiment show that with each generation, the inhibition zone grows smaller in diameter. Also, the higher the concentration of the antibiotic used, the bigger the diameter of the inhibition zone. This proves that the hypothesis is true and that the use of antibiotics should be avoided unless necessary.
Why do this project?
This science project is interesting and unique because it explores how bacteria can become resistant to antibiotics and how this affects our health. It also shows how the excessive use of antibiotics can lead to a longer recovery time for patients who are suffering from the infection.
Also Consider
Variations of this experiment include varying the types of bacteria and antibiotics, and varying the temperature at which the bacteria are left to incubate.
Full project details
Additional information and source material for this project are available below.Related videos
These videos explain the science behind this project and demonstrate key concepts used in the experiment.
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