1. Dipropylene Glycol Effects on Staph Survivorship
Henry Shaver
Pittsburgh Central Catholic High School
Grade 9

2. Background - Wax Candles
Research suggests scented wax candles generate indoor air pollutants
These indoor air pollutants have been shown to cause numerous health problems
Contains dangerous chemicals benzene and toulene

3. Dipropylene Glycol (DPG)
High purity product
Designed for use in odor sensitive applications
Found in perfumes, colognes, skin and hair products, deodorant and candles.
Variable in experiment

4. Microbial Flora
Present in the respiratory, urinary, and digestive tracts, as well as the skin.
Consist of mostly bacteria, and few protist and fungi
Most are harmless, but some can cause diseases
Influences human anatomy, physiology, and overall health
10^14 bacteria are harbored within and on humans

5. Gram (+) Bacteria
Most pathogenic bacteria in humans are gram (+) organisms
Simple cell wall
Some antibiotics work against the cell wall

6. Staphylococcus epidermidis (Staph)
Gram (+)
Found on skin or in nose of healthy individuals
One of the several bacterial parts of the lung microbiome
After incubation in agar, form ½ - 2 mm colonies that are easily counted
Can produce bio films
Form clusters
Normal flora of the respiratory tract

7. Rationale
Dipropylene Glycol can be emitted from candles in low concentrations
Could Dipropylene Glycol released from candles affect microflora of the human body?
Purpose: To determine the effects of Dipropylene Glycol on Staph survivorship

8. Hypotheses
Null: The various concentrations of Dipropylene Glycol will not have significant effect of Staphylococcus epidermidis survivorship
Alternative: The various concentrations of Dipropylene Glycol will significantly reduce the survivorship of Staphylococcus epidermidis

9. Materials YEPD Agar Plates
LB (Luria Broth) media (0.5% yeast extract, 1% tryptone, 1% sodium chloride)
Micropipettes
Sterile micropipette tips
Sterile dilution fluid (100mM KH2PO, 100mM K2PO4, 10mM MgSO4 1m NACL)
Staphylococcus epidermidis
Dipropylene Glycol (10% stock was made)
Vortex
Sterile test tubes and Rack
Incubator (37 ° C)
Ethanol
Side arm flask
Burner
Spreader Bars
Sharpie

10. Procedures (Liquid Pulse)
Staph was grown until a density of 50 klett spectrometer was reached. This was approximately 10^5 cells/ml.
The culture was diluted in sterile dilution fluid to a concentration of approximately 10^5 cells/ml.
Pipetted appropriate amounts of Dipropylene Glycol and Sterile Dilution Fluid into 4 test tubes.
Vortexed each test tube to obtain mixed solution
Added indicated amount of Staph to each individual test tube. Solution incubated at room temperature for fifteen minutes.

11. Chart of Concentrations0%
0.01%
0.1% 1%
SDF
8.9ml
Staph
0.1ml
DPG
0ml
0.01
1ml
0.99ml
0.9ml
Total Volume
10ml

12. Procedure (Liquid Pulse)
Pipetted 0.1mL from each test tube on the LB agar plates and spread.
Incubated plates at 37° C for 24 hours.
The number of Staph colonies were counted and recorded

13. Dipropylene Glycol Effect on Staph (Liquid Pulse)
P-value: 1.3E-6

14. Dunnett’s Test T-Value T-Crit 0.01% 2.5 2.88 Not sig 0.1% 5.2 Sig 1%
T-Value
T-Crit
 Conclusion
0.01%
2.5
2.88
Not sig
0.1%
5.2
Sig 1%
6.7

15. Conclusion
Dipropylene Glycol appeared to have a significant negative effect on Staph survivorship
In the Dunnett’s Test, every group but 0.01% showed significant variation from the control
Reject the null hypothesis at 0.1% and 1%

16. Limitations Only survivorship assessed
Spread plating may not have been synchronized (human error)
Limited number of replicates
Only one exposure time

17. Extensions Growth experiment Test different chemicals from candles
Other microbial models to assess skin and respiratory system microflora effects
Different concentrations
Synergistic effects

18. Bibliography
"Dipropylene Glycol." Honest Reviews of Anti-aging Skin Care and Beauty Products.
Web. 20 Nov
"DIPROPYLENE GLYCOL - National Library of Medicine HSDB Database." U.S.
National Library of Medicine. National Institutes of Health. Web. 20 Nov  
Presterl, Elisabeth, Miranda Suchomel, Michaela Eder, Sonja Reichmann, Andrea
Lassnigg, Wolfgang Graninger, and Manfred Rotter. "Effects of Alcohols,
Povidone-iodine and Hydrogen Peroxide on Biofilms of Staphylococcus
Epidermidis | Journal of Antimicrobial Chemotherapy | Oxford Academic." OUP
Academic. Oxford University Press, 22 June Web. 20 Nov  
"Names of Common Bacteria: The Good, the Bad, and the Ugly." Bright Hub. 28 Feb.
2015. Web. 20 Nov  

19. ANOVA

20. Rough Data 0% 0.01% 0.10% 1% Colonies 156 124 48 77 163 132 100 128
118
122 81
142
102 88 94
117
126
106 68
138
116 65
123
131 92 79
170
121
101
104