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This study examines the effects of Axe Body Spray on Staphylococcus epidermidis and Saccharomyces cerevisiae, representing different forms of microbial life. The results show that Axe Body Spray has a significant negative effect on survivorship of both staph and yeast.
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Effects of Axe Body Spray on Staph and Yeast Survivorship Michael Halahurich 11th grade, Pittsburgh Central Catholic High School, 2nd year in PJAS
Problem • Axe Body Spray is a widely used product popular especially among adolescents with unknown effects on microbial life
Microbial Flora • Little is known about the association between humans and their flora • Effects are mutualistic, parasitic, pathogenic, and commensal • Perform functions beneficial to the host, including the manufacture of essential vitamins, and the prevention of colonization by undesirable microbes • Human medicine, food, and skin products may have unintended effects on the body’s flora populations and their functions
Yeast • Saccharomyces cerevisiae • Easyto manipulate • Most commonly studied cell • Resembles advanced eukaryotic cells such as human cells in metabolism, reproduction, etc. • Used in this study to represent eukaryotic skin flora
Staph Staphylococcus epidermidis Widely studied Gram-positive bacterium Part of the normal skin microflora Various positive effects for the body Inhibition and killing of nonindigenous species
Axe Body Spray Being Tested • Axe Twist Body Spray • Components • Alcohol Denat., Hydrofluorocarbon 152A, Fragrance (Parfum), PolyaminopropylBiguanide Stearate.
Purpose • The purpose of this experiment is to determine the effects of Axe Body Spray on two different forms of microbial life—Staphylococcus epidermidisand Saccharomycescerevisiae.
Hypothesis • Null hypothesis: Axe Body Spray will not have a significant effect on staph and yeast survivorship. • Alternate hypothesis: Axe Body Spray will have a significant effect on staph and yeast survivorship.
Materials • Saccharomyces cerevisiae • Staphylococcus epidermidis • Micropipettes • Micro Rack • Micro Tubes • Agar Plates • Vortex • Incubator • Spreader Bars • Ethanol • Bunsen Burner • Axe Twist Body Spray • Sterile Water • Sterile Pipette Tips • 60 YEPD Agar plates (1% yeast extract, 2% peptone 2% glucose, 1.5% agar) • YEPD Media (1% yeast extract, 2% peptone, 2% glucose) • Sterile dilution fluid (10 mM KH2PO4, 10mM K2HPO4, 1mM MgSO4, 0.1 mM CaCl2, 100 mM NaCl)
Procedure • Microbes were grown overnight in sterile YEPD media • A sample of the overnight culture was added to fresh media in a sterile sidearm flask • The culture was incubated at 30 degrees Celsius until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of approximately 107 cells/mL • The cell culture was diluted in sterile dilution fluid to a concentration of approximately 105 cells/mL • Test tubes were made with concentrations of 0%, 0.1%, 1%, and 10% Axe. (5 replicates for each of the four concentrations – 20 plates per microbe)
Procedure cont. 6. The tubes were incubated at room temperature for 15 minutes 7. Tubes were vortexed and 0.1 mL aliquots were plated onto YEPD agar 8. Plates were incubated at 30 degrees Celsius for two days and colonies were counted. Each colony was assumed to have arisen from a single cell.
Procedure (Agar Infusion) Steps 1-4 from the previous procedure were repeated • Ten agar plates were treated with a “low concentration” of Axe (20 microliter of Axe, 180 microliters of water) • Ten agar plates were treated with a “high concentration” of Axe (200 microliters of Axe) • Plates were incubated for 15 minutes • Five “high concentrations” and five “low concentrations” were treated with 100 microliters from the yeast control tube • Five “high concentrations” and five “low concentrations” were treated with 100 microliters from the staph control tube • Plates were incubated at 30 degrees Celsius for two days and colonies were counted. Each colony was assumed to have arisen from a single cell
Agar Infusion Concentration Note: These amounts were directly pipetted onto the respective agar plates
A-Nova/Dunnett's Test • A-Nova: • Statistical test that allows for the comparison of means of different groups to determine significant variation • Dunnett's Test: • A follow up test used to find out which variable groups produced significant variation compared to a control
P-value: 3.94E-13 P-value: 4.8E-14
Dunnett’s Test Results t-crit = 3.239
P-value: 8.11E-06 P-value: 1.74E-08
Dunnett’s Test Results (Agar Infusion) t-crit = 3.885
Interpretation of Results • The null hypothesis can be rejected • The alternate hypothesis can be accepted • Axe Body Spray produced a significant negative effect on yeast and staph survivorship • Statistical analyses supported a significant effect at all concentrations
Interpretation of Results (Agar Infusion) • The null hypothesis can be rejected for the “high” concentrations of Axe • The alternate hypothesis can be accepted for the “high” concentrations of Axe • Exposure to Axe Body Spray via agar infusion produced a significant negative effect on yeast and staph survivorship • Statistical analyses supported significant effects at high concentrations
Limitations • Slight positioning differences in the incubation process • Slightly desynchronized plating • Limited concentration exposures • Only survivorship tested, not growth or other parameters • Study does not account for other factors that might affect the skin microbial flora
Extensions • Addition of more microbial models such as E-coli • Would allow for a gram-positive vs. gram-negative comparison • Other brands of body spray could be used for further analysis • Different concentrations of the variable could be tested
Bibliography • http://davidmlane.com/hyperstat/B112114.html • http://wiki.yeastgenome.org/index.php/What_are_yeast%3F • http://www.ewg.org/research/not-so-sexy • https://statistics.laerd.com/statistical-guides/one-way-anova-statistical-guide.php • http://textbookofbacteriology.net/normalflora.html • http://www.bioquell.com/en-us/resources-and-support/microbiology/staphylococcus-epidermis/