Sunday, 26 April 2015

Investigating antibiotic properties

This experiment investigates how some common household items can work as antibacterial agents.


Any experimentation with living bacteria requires strict aseptic technique. It is assumed you will be familiar with these techniques prior to completing this experiment - if not advice can be found at

In general ensure that hands are washed before and after completing any work with bacteria and that all implements used are sterile. Additionally plates should not be opened once incubated and should be disposed of in an autoclave.


Use a poured plate with the bacterial strain being used already present in the agar.

Select a number of household items, such as hand soap, dish soap, bleach, mouthwash and use forceps to dip a small disk (up to 1cm diameter maximum) into the liquid and place on the surface of the agar. A disk dipped in boiled water should also be used as a control. To allow easy identification use a pencil to number the disks prior to dipping.

Set up three plates in exactly the same way, then leave to incubate for up to a week.

Measure the furthest distance from the edge of each disk to the bacteria now visible to determine the most effective antibacterial substance.