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

Pustule - an inflamed red circle on the skin with a white center.

Papule - a small, red, inflamed bump with no pus. Nodule - similar to a papule. It is an inflamed

elevation of the skin. Cyst - “…an abnormal membranous sac

containing a liquid or semi-liquid substance consisting of white blood cells, dead cells, and bacteria. Often very painful and they extend to deeper layers of skin” ("What Is Acne?").

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 then 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 AcidAcneFree Terminator - 2% Benzoyl Peroxide CVS Acne Treatment Gel - 10% Benzoyl

Peroxide Carbomer, Triethanolamine, and Bezoyl

Peroxide are common to the CVS brand gel and the AcneFree brand gel.

Alcohol was 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 amount of time each disc soaked in the solution, the same amount of time kept in the incubator, and the same kind of Petri dishes and discs.

PROCEDURE

1. Fill 6 dishes with agar using sterile technique2. Hydrate bacteria using sterile technique3. 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 with

3 different acne medications and one with just sterile water.

8. Let discs soak.

PROCEDURE9. Swab S. epidermidis bacteria on the agar using

sterile technique.10. After discs soak for 20 minutes, put a disc

from each of the 3 mixtures and one of water in each of the 6 Petri dishes with bacteria.

11. Each dish should have 4 discs in it. 12. Tape Petri dishes.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 20 50 30 10

Trial 3 20 40 30 10

Trial 4 20 40 25 10

Trial 5 20 40 25 10

Trial 6 25 40 25 10

Average 21 43 28 10

StDev 1.9 4.7 2.5 0

Neutrogena Acne Free CVS Water0

5

10

15

20

25

30

35

40

45

50

The Affect of Acne Medication on the Growth of S. epidermidis

bacteria

Solutions

Aver

age

Zone

s of

Inhi

biti

on

(mill

imet

ers)

RESULTS CONTINUEDANOVA SUMMARY :

Groups Count Sum Average Variance

Column 1 6 125 20.83333 4.166667

Column 2 6 260 43.33333 26.66667

Column 3 6 165 27.5 7.5

Column 4 6 60 10 0

*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 medication 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 make a difference because the temperature of the skin is close 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 very effective in removing dirt and oil from the skin and preventing the growth of acne.

REFERENCES

"Acne: Common Causes." Doctorgoodskin.com. N.p., n.d. Web. 21 Nov. 2010.      <http://www.doctorgoodskin.com/ds/acne/commoncauses.php>.

"Acne: How Acne Forms?" Doctorgoodskin.com. N.p., 14 June 2006. Web. 21 Nov.      2010. <http://www.doctorgoodskin.com/ds/acne/howacneforms.php>. 

"How Acne Develops." Mayoclinic.com. N.p., 1998. Web. 18 Nov. 2010.      <http://www.mayoclinic.com/health/medical/IM02434>. 

"Ingredients that Causes Acne." Quickacneremedy.com. Quick Acne Remedy, LLC,      2003. Web. 16 Nov. 2010. <http://www.quickacneremedy.com/acne-articles/      ingredients-that-causes-acne.html>.

Mayo Clinic staff. "Over-the-counter Acne Products: What Works and Why."      Mayoclinic.com. N.p., 16 Apr. 2010. Web. 18 Nov. 2010.      <http://www.mayoclinic.com/health/acne-products/SN00039>.

"6 Common Ingredients in Acne Products You Should Know." 10acne.com. N.p., 2006.      Web. 18 Nov. 2010. <http://www.10acne.com/      acne_treatment_article22.html>.

"What Is Acne?" Acnegroup.org. N.p., n.d. Web. 1 Dec. 2010.      <http://www.acnegroup.org/aboutacne.php4>.