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Testing the effectiveness of various anti microbial agents.

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Testing the effectiveness of various anti microbial agents. Aim: ~ We are trying to find out what bleach solutions and other solutions will work best at killing Microcuccul luteus (safe bacteria). Apparatus: ~ 2 Petri dishes per person Ethanol Scalpel Cork borer Bleach solutions Other substances of your own choice Bunsen burner Protective mat Cotton wool Pipette Predictions:~ I predict that: Prediction 1:~ 20% bleach will be the best anti-microbial agent. Prediction 2:~ Toothpaste will have a large inhabitation zone. Prediction 3:~ Water would have the worst inhabitation zone. Method: ~ *Firstly you need to sterilise the whole area and all of the equipment with ethanol. This is done so that no microbes can get into the safe bacteria environment unless it is absolutely necessary. Your hands must be washed with soap so that they do not have any bacteria on them. *Once this is done you need to sterilise your cork borer. You do this by dipping it in ethanol and putting up against a half roaring flame. Hold the cork borer down in to the flame at an angle, as there is a risk that the flame may come up the middle of it and burn the users hand. *Now you need to put four holes in the agar jelly (look at diagram 'A'). They will be the same size (ours was 10mm) ...read more.


2nd (mm) 3rd (mm) 4th (mm) Average (mm) 0% (water) 0 0 0 0 0 1% 14 15 16 16 15.25 5% 18 19 19 21 19.25 10% 28 25 25 22 25 20% 22 27 28 27 26 Other 1st (mm) 2nd (mm) 3rd (mm) 4th (mm) Average (mm) Bleach (10%) 28 25 25 22 25 Water 0 0 0 0 0 Duzzit 20 21 20 20 20.25 Listerine 12 11 13 11 11.75 Dettol 40 38 45 38 40.25 My results: ~ Look at diagram 'C' and 'D' Analysis: ~ My results show me that the higher the concentrate of bleach the more bacteria was killed. I predicted that this would happen, and the results now reinforce my prediction. However it is difficult to see any particular pattern in the class results of the different substances. We can see that Dettol was the strongest, so the best at killing Microcuccul luteus. On the other hand we can see that water and Listerine were the weakest, so the worst at killing Microcuccul luteus. Conclusion: ~ The reason that we knew that Microcuccul luteus was produced was because you could see small round dots on the agar jelly. Because of this you were then able to find the inhabitation zone. This is when the bacteria have been killed and there is now a clear zone. ...read more.


When measuring the diameters of the inhabitation zones people may perceive it very differently. For instance one person may think that a measurement is closer to on half i.e. if 4.5mm they may perceive it as 5mm. This will effect the results because all were taken in mm, so a good eye is needed to get an exact measurement. People will judge the outside of the exclusion zones differently. To make it a fair test you would only put one anti-microbial agent in an agar plate. This would mean that it is easy to see the inhabitation zone thus resulting to easier measurements. You could extend this experiment by using a wider variety of anti-microbial agents. not only could you use household products, you could you industrial products and see what results you would get using them. You would then be able to compare the results and see what type of products work better. You could also find a list of the most popular household products and test theses against each other. This would be helpful for people interested in buying products that kill a wide range of bacteria and they could see what works best. Another experiment that you could do to test the effectiveness of anti-microbial agents is to get a test area, for instance a kitchen floor. You would then be able to clean parts of his floor with different agents. You would take a swap of the area before and after cleaning it and see what product worked the best. ...read more.

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