Project cost ($):
1 day for preparation, 8 days for the science project experiment
Access to laboratory equipment (eg. petri dishes)
Always follow laboratory safety guidelines and always practice sterile technique when handling microbes. Never have any food or drink at your workstation and always thoroughly wash your hands with disinfectant soap or alcohol before leaving your workstation. Always dispose of used material in a biohazard bag. If none are available, the bacteria should be destroyed with bleach before being disposed of.
Table of Contents
The aim of this science fair project is to find out how the concentration of disinfectants can affect bacteria resistance. The experiment is carried out using different concentrations of Dettol disinfectant.
Lower disinfectant concentrations cause the bacteria to develop resistance more quickly.
Bacteriaresistance, microorganisms, evolve, genetic, mutation, zone of inhibition
The materials required for this science fair project are:
1. The independent variable for this experiment is the concentration of dettol disinfectant used – 25%, 50% and 75%. The dependent variable is the size of the inhibition zone which refers to the area free of bacteria). This is determined by measuring its diameter using a ruler. The constants (control variables) are room temperature, amount of sunlight and the ingredients in the Petri dish agar.
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.
Plot your results into a graph as shown below
The hypothesis that a lower concentrationof disinfectant accelerates the development of bacteria resistance is is proven to be false. However, it takes a long period of time before bacteria resistance may be observed, hence this experiment may have to be repeated many times over for any observable results.
The excessive use of disinfectants can engender bacteria resistance such that the disinfectant becomes ineffective in killing bacteria. The development of more resistant strains of bacteria means that stronger concentrations of disinfectants have to be used in order for it to be potent in controlling bacteria growth. This may have adverse consequences as strong concentrations of disinfectants are harmful to humans and the environment.
The science fair project can be repeated by varying the types of disinfectants used, such as antibacterial soaps, Listerine or bleach.Try testing the resistance of various other kinds of bacteria.
Why is bacillus resistant to disinfectants? - http://www.ehow.com/how-does_5173187_bacillus-resistant-disinfectants_.html