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Effectiveness of Antibacterial Hand Soap against E. Coli

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Krista Rasmussen

on 2 December 2013

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Transcript of Effectiveness of Antibacterial Hand Soap against E. Coli

A Study on The Effectiveness of Antibacterial Hand Soap against E. Coli
When various hand soaps are applied to E. Coli bacteria, the growth of the E. Coli bacteria could be prevented because the active ingredients in the hand soap could have antibacterial qualities and therefore would prevent the formation and reproduction of the E.Coli.

We think Dial Compete will create the largest zone of inhibition because the active ingredient, Triclosan is both antibacterial and antifungal.
Triclosan targets bacteria primarily by inhibiting the synthesis of fatty acid.
Triclosan will exhibit larger zone of inhibition compared to the Avalon Organics and Lysol because Avalon Organic only targets bacteria by destroying it by its acidity (low pH level), and the active ingredient in Lysol, Benzalkonium Chloride, only breaks the lipid bilayers of the bacteria.
Triclosan will create a larger zone of inhibition because without the formation of the fatty acids in the first place, the reproduction and replication of cell membranes will be impossible.
Krista Rasmussen
Winnie Liao

Overview of Experiment
Independent Variable:
Brand/Active Ingredients in Hand Soaps: Triclosan, Benzalkonium Chloride, Lemon
Dependent Variable:
Radius of zone of inhibition (mm).
We used quantitative variables to measure the dependent variable.
Experimental Replicates:
Three agar plates with bacteria and four sections including control, Triclosan, Benzalkonium Chloride, and Lemon were tested.
Experimental Design
Controlled Experiment
Each soap was diluted in order to reduce viscosity:
1) Label three test tubes with each soap brand.
2) Measure/Add 2 mL of each soap into respective labeled test tubes.
2) Measure/Add 2 mL water to each test tube.
3) Shake well by plugging with thumb and shaking until consistent throughout.
2 mL Soap
2 mL DI water
To identify the effectiveness of antibacterial hand soaps in killing/stopping the growth of E. Coli bacteria on hands by utilizing different active ingredients in three popular hand soaps.
Three Hand Soaps/Active Ingredients:
Dial Complete: Triclosan
Avalon Organics: Lemon
Lysol: Benzalkonium Chloride.

Kirby-Bauer Disc Diffusion Method:
Applied products to E-Coli
Observed the zone of inhibition in
a time frame of one week.
Why should you wash your hands?
Importance of Washing Hands
Keeping hands clean is one of the most important ways to prevent the spread of infection and illness (CDC).
In healthcare settings, hand hygiene can prevent potentially fatal infections from spreading from patient to patient and from patient to healthcare worker and vice-versa (CDC).
Mechanisms of Action
E. coli (Escherichia coli)
Live in the intestines of healthy people and animals
Most strains of E. coli are harmless (MAYO Clinic)
Some kinds of E. coli are not and can cause:
Urinary tract infections
Respiratory illness
Hemolytic uremic
Active Ingredient:
Benzalkonium Chloride
Mechanism of Action:
Denatures bacteria by breaking the lipid bilayers of the bacteria.
Brand: Dial
Active Ingredient:
Mechanism of Action:
Inhibits the synthesis of fatty acids.
Brand: Avalon Organics
Active Ingredient: Lemon
Mechanism of Action: Denatures bacteria by its acidity causing catalytic properties to halt, preventing metabolism. (Lemon=low pH level).
Sterile Water
Dial Complete
Avalon Organics
Figure 1. Zones of Inhibition of each quadrant on each plate with standard deviation.
Kirby-Bauer Disc Diffusion Method
Figure 2. Photo of Plates depicting the zones of inhibition of each brand of soap.
Zones of Inhibition in Descending Order
1) Dial complete with Triclosan had the largest zone of inhibition (Mean=40)
2) Lysol with Benzaclonium Chloride (Mean=36.33)
3) Avalon Organics with Lemon (Mean=20.33)
Gram Stain
Turned Pink-Gram negative
Thin layer of peptidoglycan in the cell wall
Have outer lipopolysacharide layer (more complex cell wall)
Triclosan is the most effective antibacterial agent as evidence by the fact that on average, it caused the largest zone of inhibition. (HYPOTHESIS CORRECT)
Benzaclonium Chloride is the second best antibacterial agent because it caused an only slightly smaller zone of inhibition.
Due to the fact that the gram stain was negative it is clear that Triclosan and Benzaclonium Chloride are able to effectively penetrate the liopolysacharide layer of the cell wall.
This test showed that synthetic chemicals are more effective at fighting off bacteria than naturally occurring substances.
Lemon, though effective in fighting off E.Coli is the least effective.
Sources of Error
Plate three: Quadrant one
The control (DI water) had a zone of inhibition meaning that we probably dipped the sterile paper disc into one of the soaps
Most likely lemon because zone of inhibition was consistent with the other lemon quadrants
Because we had to dilute the soaps this test did not accurately portray how the normal concentrations of each soap act against E.Coli
The time constraint of one week does not depict how these antibacterial agents work over a long period of time
This experiment only tested one strain of E.Coli
Did not study pathogenic bacteria, which is what hand washing aims to particularly kill off
Future Directions
Study the effectiveness of hand soap against pathogenic strains of E.Coli
Study the long & short term effectiveness of hand soap on battling bacteria
ie. how many hours does the hand soap stay on your skin, killing off bacteria?
Study the negative effects of using synthetic chemicals on skin.
ie. futher research on the impact of Triclosan on hormone levels
Information on Active Ingredients
Triclosan: ("Triclosan: What consumers should know," 2013)
Not currently known to be hazardous to human
Needs further review
Animal studies & hormone regulation
Making bacteria resistant to antibiotics
Benzalkonium Chloride ("Benzalkonium chloride ," 2007)
Long term exposure results in asthma and immune system disorders
Lemon ("Find a vitamin or supplement-lemon," 2009)
Generally no harm
Treats common cold & flu
Side effects of higher dosage unknown
Applying to skin may cause sunburn

Different antibacterial agents are more effective than others at actually cleaning your hands
Picking the right soap is important!
Hand soap is vitally important to health.
Benzalkonium chloride – unsafe in any product. (2007, July 25). Retrieved from http://cleanwelltoday.com/blog/?p=61
Blamire, J. (2000). Effect of ph on growth rate. Retrieved from http://www.brooklyn.cuny.edu/bc/ahp/CellBio/Growth/MGpH.html
Centers for disease control and prevention. (2013, March 25). Retrieved from http://www.cdc.gov/features/handwashing/
Find a vitamin or supplement-lemon. (2009). Retrieved from http://www.webmd.com/vitamins-supplements/ingredientmono-545- LEMON.aspx?activeIngredientId=545&activeIngredientName=LEMON
MMWR. (2012, October 25). Clean Hands, Healthy Body. A Minute of Health with CDC. Podcast retrieved from http://www2c.cdc.gov/podcasts/player.asp?f=8626036
Triclosan: What consumers should know. (2013, September 24). Retrieved from http://www.fda.gov/forconsumers/consumerupdates/ucm205999.htm
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