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The effect of antibacterial toothpastes on Micrococcus luteus

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The effect of antibacterial toothpastes on Micrococcus luteus 24.05.2009 Research question What effect do antibacterial toothpastes, such as blend-a-med and Colgate, have on Micrococcus luteus? Introduction Preliminary work revealed that both toothpastes have an antibacterial effect on Micrococcus luteus. According to the preliminary study, the zone of inhibition of blend-a-med was slightly bigger than Colgate's. Therefore the antibacterial effect of blend-a-med is greater than Colgate's. Both toothpastes contain an antimicrobial ingredient Triclosan which kills many harmful bacteria. Triclosan ultimately results in a breakdown or failure in the bacteria's cell wall. Cell wall failure affects bacteria's most vital survival processes including uptake of nutrients, inhibition of amino acid incorporation, inhibition of uracil incorporation, as well as causing membrane lysis.1 The antibacterial effect of toothpastes is an important factor for evaluating the benefits it has on health but it should also be considered that Triclosan and Fluoride might potentially be harmful to the user when taken in large quantities.2 The preliminary study also revealed that the toothpaste should be mixed with water, so that it would be well transferrable with a pipette. (It should also be mentioned that the toothpaste which is sold under the name of "blend-a-med" in some of the European countries, is known as "Crest" in the United Kingdom.3 ) Independent variable * The type of toothpaste used in the agar plates filled with M. luteus. - "Colgate Total" and "blend-a-med + eucalyptus" Dependent variable * Zone of inhibition on the M.luteus around the toothpaste in millimetres. ...read more.


5. Sterilise the cork borer in the flame. 6. Wait until the cork borer is not hot - otherwise it will melt the agar. 7. Cut uniform 'wells' in the agar plate with the cork borer. 8. If necessary, use the mounted needle to pull the cut piece out. 9. Mix both toothpastes with an equal amount of sterile distilled water in the measuring cylinder. 10. Use the pipette to transfer the two mixtures into the agar plates. 11. Change the pipette after every four plates to guarantee that the pipette is not contaminated with bacteria. 12. Repeat the procedure with each agar plate. 13. Tape all the plates up to avoid other bacteria contaminating the samples. 14. Leave the plates in an incubator at 30 degrees for 24 hours. 15. Measure the zones of inhibition so that two diameters will be recorded with the digital measurer The effect of antibacterial toothpastes on Micrococcus luteus Size of zone of inhibition in millimetres Raw data Error: +/- 0.005 mm Number of repeat Diameter blend-a-med blend-a-med mean values of two diameters Colgate Colgate mean values of two diameters 1 Diameter I 19,06 14,43 18,50 18,87 Diameter II 19,80 19,24 2 Diameter I 21,23 22,25 19,91 20,03 Diameter II 23,27 20,15 3 Diameter I 22,00 21,77 20,48 20,62 Diameter II 21,53 20,76 4 Diameter I 24,23 25,90 22,78 22,04 Diameter II 27,58 21,30 5 Diameter I 24,57 24,84 23,01 23,13 Diameter II 25,10 23,24 6 Diameter I 25,41 25,50 23,44 23,63 Diameter II 25,58 23,82 7 Diameter I 26,33 25,31 22,27 22,31 Diameter II 24,28 22,34 8 Diameter ...read more.


A sufficient number of repeats were made and every repeat indicated that the inhibition zone of "blend-a-med" is bigger than the inhibition zone of "Colgate." The mean values and the Student-T test also indicated that there was significant difference between the two sets of data. Therefore the conclusion is reliable. Procedure weaknesses The concentration of water in either toothpaste may not have been the same. Therefore the concentration of the samples was not the same. This weakness can be improved by not using water in the test or by measuring the exact volume of the toothpaste and mixing it with the same volume of water. The application of the toothpaste can be done more carefully by squeezing the pipette from the part which is closest to the plate. The amount of bacteria put on each plate can be measured more precisely with a pipette The amount of agar in each plate can be measured more precisely by using a measuring cylinder. To apply toothpaste to the plate by a pipette, it is necessary to mix toothpaste with water. The density of the toothpaste is very different from the density of water and the mixture will not be uniform. Therefore the concentration of toothpaste depends on the depth from which the sample is taken. The problem can be improved by mixing the solution continuously to get a uniform solution. Procedure limitations The chemical Triclosan is not present in the entire tube at the same concentration. Therefore different samples which are taken from different parts of the toothpaste tube may have a different amount of Triclosan. ...read more.

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