The Effect of Acne Medication on the Growth of S. Epidermidis bacteria

Types of Acne Comedo - when a follicle is clogged with dirt, bacteria, and dead skin cells. Blackheads Whitehead Papule - a small, red, inflamed bump with no pus. Pustule - an inflamed red circle on the skin with a white center. Nodule - It is a large, inflamed elevation of the skin. Often very painful. Cyst – similar to a nodule, but it is has pus and is usually larger than a nodule.

Background Each hair follicle on the skin contains a sebaceous gland which produces sebum. Sebum is an oily substance that coats the skin and protects it. Acne is formed when dead skin cells and dirt clog the pore and sebum starts to build up in the follicle. Then Propionibacterium acnes (P.acnes) infects and multiplies inside the sebum.

Question What is the effect of acne medication on the growth of S. epidermidis bacteria?

Hypothesis Acne medication with the highest percentage of the main anti-acne ingredient will have the largest effect on the growth of bacteria and therefore the largest zones of inhibition.

Materials 3 different acne medications 6 Petri dishes prepared with agar 6 sterile swabs 16mL of sterile water Culture of S. epidermidis bacteria 24 discs 4 empty Petri dishes 4 pipettes Incubator Gloves Lab coat Balance Tweezers Tape Bunsen Burner Timer Goggles Sharpie marker

Acne Ingredients Active Ingredients: Neutrogena Rapid Clear Gel - 2% Salicylic Acid AcneFree Terminator - 2% Benzoyl Peroxide CVS Acne Treatment Gel - 10% Benzoyl Peroxide Carbomer, Triethanolamine, and Benzoyl Peroxide are the common ingredients in the CVS brand gel and the AcneFree brand gel. Alcohol is present in both Neutrogena brand gel and the AcneFree brand gel. Water is present in all 3 acne medications. In addition, the acne medications all have other excipients.

Variables Independent variable: The different types of acne medication Dependent variable: The size of the zones of inhibition Control variable: A disk soaked in 4mL of sterile water and no acne medication Constant variables: The type of bacteria, the same amount of acne medication and water in each solution, the same temperature of the surrounding air, the same kind of Petri dishes and discs, the same amount of time each disc soaked in the solution, and the same amount of time kept in the incubator.

Procedure 1. Fill 6 dishes with agar using sterile technique 2. Hydrate bacteria using sterile technique 3. 24 hours later; label all 6 Petri dishes. 4. Weigh 1 gram of the first acne medication and mix it with 4mL of sterile water in an empty Petri dish. 5. Repeat step 4, 2 more times using a different acne medication each time. 6. Put 4mL of sterile water in an empty Petri dish. 7. Put 6 discs in each of the 4 empty Petri dishes, 3 of which contain different acne medications and one with just sterile water. 8. Let discs soak.

Procedure 9. Swab S. epidermidis bacteria on the agar using sterile technique. 10. After discs soak for 20 minutes, put a disc from each of the 4 Petri dishes with solutions in each of the 6 Petri dishes with bacteria. 11. Each dish should have 4 discs in it. 12. Tape Petri dish lids. 13. Let the 6 Petri dishes sit in the incubator for 24 hours. 14. Measure the zones of inhibition after 24 hours. 15. Autoclave the dishes and then dispose of them.

Zones of Inhibition (millimeters)   Neutrogena AcneFree CVS Water Trial 1 20 50 30 10 Trial 2 Trial 3 40 Trial 4 25 Trial 5 Trial 6 Average 21 43 28 StDev 1.9 4.7 2.5

Results Continued *ANOVA P-value = 5.08E-13 * T-Test : ANOVA SUMMARY : Groups Count Sum Average Variance Column 1 6 125 20.83333 4.166667 Column 2 260 43.33333 26.66667 Column 3 165 27.5 7.5 Column 4 60 10 *ANOVA P-value = 5.08E-13 * T-Test : Neutrogena v. CVS 0.0007447 Water v. Neutrogena 1.3715 E-07

Limitations These results may differ if a different type of bacteria is used. Even though sterile technique was used throughout the experiment there is always the risk of contamination. Medications that had volatile materials such as alcohol may have evaporated upon incubation. Discs may not have absorbed at the same rate.

Continuation To further this experiment different bacteria such as P.acnes could be used. In addition, acne medication with other types of active ingredients could be used as well as prescription medications or natural remedies. Testing humans with acne would be ideal, but hard for me or other high school students to obtain. Incubation at room temperature could possibly make a difference because the temperature of the skin is closer to room temperature. Another idea for continuation would be to isolate ingredients so it is just one active ingredient with no excipients.

Conclusion AcneFree brand gel (2% Benzoyl Peroxide) had the largest zones of inhibition compared to the CVS brand gel (10% Benzoyl Peroxide) and the Neutrogena brand gel (2% Salicylic Acid). One possible explanation for why Benzoyl Peroxide did better than Salicylic Acid in this experiment is because Benzoyl Peroxide acts as an anti-bacterial that removes bacteria in the follicles, while Salicylic Acid slows down the process of skin cells shedding inside the hair follicle which clogs the pores.

Conclusion The AcneFree brand which only had 2% Benzoyl Peroxide might have done better in killing the bacteria than the CVS brand with 10% Benzoyl Peroxide possibly because the AcneFree Brand contained alcohol which is effective in removing dirt and oil from the skin and preventing the growth of acne.

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