Practice Assignment 04
Comparing mouthwash activity
Mouthwashes contain chemicals to reduce the number of unwanted micro-organisms in the mouth. Manufacturers test their products to see how well they stop micro-organisms growing. One method of doing this is to put some test substance onto an agar plate which has been inoculated with a microbial culture. The substance diffuses into the agar. If the substance prevents the growth of micro-organisms the agar will show a clear zone, free of micro-organisms, after incubation.
There are many different anti-microbial agents used in the wide range of mouthwashes on sale in the shops.
What you have to do
- You will work in one of four groups. Three of the groups will each take a different brand of mouthwash to test at three different dilutions. The fourth group will test the three brands at their recommended strength. Each person in your group should carry out the test on the same three samples.
- Get a copy of the Standard Procedure SP 0004:2005.
- Follow the procedure and your group instructions to test the activity of the mouthwash.
- Compare your test report with the rest of your group. Prepare a group report.
- Discuss the reports from all four groups. Prepare a class report comparing the anti-microbial activity of the three mouthwashes tested.
Some hints
- It is important to use aseptic techniques. Make sure that you know exactly what you are going to do before you start.
- Each person in your group is testing the same samples. If you work carefully the results should be similar.
Some questions
- Why would it be useful to do all the tests again using a different micro-organism?
- Why do mouthwashes contain anti-microbial substances?