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Diseases Science Fair Project

Bacteria Resistance and Disinfectant Concentration

Bacteria Resistance and Disinfectant Concentration | Science Fair Projects | STEM Projects
Have you ever wondered how bacteria can become resistant to disinfectants? In this science project, you will explore the effects of different concentrations of disinfectant on bacteria growth. You will observe the size of the inhibition zone, which is the area free of bacteria, and measure its diameter.


The hypothesis is that lower disinfectant concentrations cause the bacteria to develop resistance more quickly.

Method & Materials

You will prepare 12 Petri dishes of agar, mix different concentrations of dettol disinfectant with water, and rub a swab of bacteria culture all over the agar surface of the Petri dishes. You will then place filter paper discs in the middle of the Petri dishes and observe the results after two days.
You will need 12 agar Petri dishes, 12 disinfected swabs, a bottle of disinfected water, a filter paper, a hole puncher, 4 test tubes, a measuring cylinder, a bottle of dettol disinfectant, a beaker of water, E. Coli bacteria culture, a pair of sterile forceps, and a marker pen.


The results show that a higher concentration of dettol disinfectant result in a larger inhibition zone. However, there is no significant change in the relative sizes of the inhibition zones after 4 generations, indicating no change in bacteria resistance.

Why do this project?

This science project is interesting because it explores the effects of different concentrations of disinfectant on bacteria growth. It also demonstrates the concept of the Kirby-Bauer disk diffusion method, which is used by microbiologists to assess the effectiveness of antimicrobial agents.

Also Consider

Variations of this experiment include testing the resistance of various other kinds of bacteria, and using different types of disinfectants such as antibacterial soaps, Listerine or bleach.

Full project details

You can find additional information and details for this science fair project here. Have fun exploring!

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