Transcript Antimicrobial Effects of Sunscreen

ANTIMICROBIAL
EFFECTS OF
SUNSCREEN
Michael DeSantis
Freshman
Central Catholic High School
PROBLEM
• An estimated 10% of human body mass is
composed of symbionts.
• The human microbial flora performs many
functions vital to human health.
• Does application of sunscreen have any effects
on the human microbial flora?
PREVIOUS STUDIES
• Sunscreens containing vitamin A have been
linked to the acceleration of tumor
development by the FDA.
• Effects linked to active ingredients in
Coppertone sunscreen include:
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Acceleration of breast cancer cell growth
Rashes
Allergic reactions
Low-birthweight babies
Hormone disruption
SUNSCREEN
• Commonly used topical ointment for help to
prevent sunburn.
• Prevents sunburn by reflecting or absorbing
ultraviolet radiation from the sun.
• Uses organic chemicals and particulates to absorb
UV light.
• Uses inorganic particulates to reflect or scatter UV
light.
• Coppertone active ingredients: homosalate,
octinoxate, octisalate, oxybenzone.
HUMAN FLORA
• Comprised of all the microorganisms that reside
in or on the human body (examples: skin,
saliva, gut).
• Most species are non-pathogenic
microorganisms that either have no effect on
the host or offer some benefit.
• Almost 1000 species of bacteria live in the gut
of an average human body.
SKIN FLORA
• Comprised of all microorganisms of the human
flora that live on the skin.
• 1 trillion bacteria live on or in the skin of an
average human.
• Stimulates the skin's immune system by the
prevention of colonization by pathogenic
microorganisms.
Escherichia coli (E. coli)
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Cells are rod shaped and usually about 2 micrometers in length.
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Part of the human flora; found in the human colon and digestive tract.
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One of the most studied and widely understood types of bacteria.
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Reproduces rapidly, often within thirty minutes.
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Commonly used as a prokaryote cell model.
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Many strains, most non-pathogenic.
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Utilized in this test as model for prokaryotic members of the human
microbial flora.
PURPOSE
• To assess the effects of sunscreen
on the survivorship of E. coli bacteria
colonies.
HYPOTHESES
• Null Hypothesis: Sunscreen will not have a
significant effect on E. coli survivorship.
• Alternative Hypothesis: Sunscreen will have a
significant effect on E. coli survivorship.
MATERIALS
• Coppertone SPORT:
SPF 30 Sunscreen
• E. coli (DH5-alpha)
• LB media and agar
plates (0.5% yeast
extract, 1% tryptone,
1% sodium chloride)
• Incubator
• Klett spectrophotometer
and sidearm flasks
• Micropipettes
• Vortex
• Labeling tape
• Ethanol, spreader bar,
• Sterile capped test
matches, turntable
tubes with Sterile
Dilution Fluid (100mM
KH2PO4, 100mM
K2HPO4, 10mMMgSO4,
1mM NaCl)
PROCEDURE
1. E. coli was grown overnight in sterile LB media.
2. A sample of the overnight culture was added to fresh LB
media in a sterile sidearm flask.
3. The culture was incubated until a density of 50 Klett
spectrophotometer units was reached. (Representing a
cell density of approximately 108-109 cells/mL.)
4. The culture was diluted in sterile dilution fluid to a
concentration of approximately 105 cells/mL.
5. The sunscreen was diluted with sterile dilution fluid in
test tubes into concentrations of 10%, 1%, and 0.1% with
a fourth tube containing 0% of the sunscreen to be used
as a control to a total volume of 10 mL.
PROCEDURE
CHART OF CONCENTRATION
0%
Sunscreen
(control)
0.1%
Sunscreen
1%
Sunscreen
10%
Sunscreen
SDF
10 mL
9.99 mL
9.9 mL
9 mL
Sunscreen
0 mL
0.01 mL
0.1 mL
1 mL
Total
10 mL
10 mL
10 mL
10 mL
6. 0.2 mL aliquots of each solution was spread onto LB
agar plates.
7. E. coli (approximately 300 cells) was spread onto each
plate.
8. The plates were left to sit overnight.
9. The resulting colonies were counted.
Sunscreen Effects on E. coli Survivorship
P-value
350
0.036639
Number of Colonies
300
250
200
150
100
50
0
0%
0.10%
1%
Concentration of Sunscreen
10%
DUNNETT’S TEST ANALYSIS
T Critical = 3.10 (significant difference)
Alpha = 0.05
Variable
Concentration
T value
Interpretation
0.1% Sunscreen
0.62
Not Significant
1% Sunscreen
0.3
Not Significant
10% Sunscreen
2.87
Not Significant
CONCLUSIONS
• The null hypothesis that sunscreen does not
affect the survivorship of E. coli was accepted
for the 0.1%, 1%, and 10% concentrations.
• None of the concentrations of sunscreen
appeared to significantly affect the survivorship
of E. coli colonies compared to the control.
LIMITATIONS AND EXTENSIONS
LIMITATIONS
• The sunscreen was very insoluble and difficult to mix into the SDF.
• Only one type of sunscreen was used.
• The plating was not perfectly synchronized.
EXTENSIONS
• A normal skin flora, Staphylococcus epidermidis,
will be utilized in the coming weeks, representing
gram positive skin flora.
• Test different brands of sunscreen.
• Test different concentrations of sunscreen.
• Test sunscreen on different cellular models.
• Test different topical solutions and ointments for antimicrobial
effects.
REFERENCES
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http://www.cosmeticsdatabase.com/product.php?prod_id=241521
http://www.aolnews.com/2010/05/24/study-many-sunscreens-may-beaccelerating-cancer/
http://www.grouptrails.com/Sunscreens.htm
http://microbezoo.commtechlab.msu.edu/zoo/zah0700.html
http://www.time.com/time/specials/packages/article/0,28804,1976909_197
6895_1976897,00.html
http://sciencenow.sciencemag.org.libproxy.ucl.ac.uk/cgi/content/full/scienc
enow;2009/528/1
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.chapter.500
http://www.ncbi.nlm.nih.gov/pubmed/18275522
http://dx.doi.org/10.1126%2Fscience.1171700
http://textbookofbacteriology.net/normalflora.html
http://www.bmb.leeds.ac.uk/mbiology/ug/ugteach/icu8/flora/cases.html
http://www.cehs.siu.edu/fix/medmicro/normal.htm
http://www.mansfield.ohio-state.edu/~sabedon/biol2035.htm
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http://www.textbookofbacteriology.net/themicrobialworld/NormalFlora.html
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NORMAL HUMAN FLORA (MICROBIOTA)
• Microorganisms that are expected to be present
in the human body to maintain health.
• Produces vitamins such as biotin and vitamin K.
• Breaks down nutrients that otherwise could not
be digested.
• Helps in prevention of allergies, illnesses, and
diseases.
• Energy absorbing potential of normal gut flora
bacteria helps in prevention of obesity.
RESULTS
COLONIES PER PLATE
0%
0.1%
1%
10%
Plate 1
280
287
277
202
Plate 2
282
297
292
254
Plate 3
346
245
248
235
Plate 4
243
295
326
232
Plate 5
316
276
316
240
Plate 6
275
279
252
286
Average
290.33
279.83
285.16
241.5
STATISTICAL ANALYSIS (ANOVA)
Anova: Single Factor
SUMMARY
Groups
0% (Control)
Count
0.10%
1%
10%
6
6
6
6
Sum
Average
Variance
1742 290.3333333 1281.866667
1679 279.8333333 360.9666667
1711 285.1666667 1042.566667
1449
241.5
766.3
ANOVA
Source of Variation
Between Groups
Within Groups
SS
df
MS
F
P-value
F crit
8889.458333
3 2963.152778 3.433847412 0.036639101 3.098391
17258.5
20
862.925
Total
26147.95833
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