Are you sure your hands are clean?
If given the choice between water only, soap and water, hand sanitizer or sanitizing wipes to clean your hands then I hypothesize that washing your hands with soap and water for 20 seconds would be the most effective way to remove the most amount of bacteria because soap lysis bacteria.
What is bacteria?
- Bacteria are prokaryotic, single celled organisms
- Lack a nucleus
- Live almost anywhere
- Among the first life forms on Earth
- Three basic shapes:
- Spherical (Coccus)
- Rodlike (Bacillus)
- Curved (Vibrio, Spirillum or Spirochete)
How can bacteria harm you?
Are all bacteria bad?
No not all bacteria are bad. bacteria that can be good can be found in.
Why is it important to get rid of the bacteria on your hands?
Germs from unwashed hands can be transferred to objects, like handrails, table tops, or toys, and then transferred to another person's hands giving them the bacteria on your hands.
Removing germs through handwashing therefore helps prevent diarrhea and respiratory infections and may even help prevent skin and eye infections.
Bacteria can enter the body through the mouth, nose, breaks in the skin and genitals.
What is the recommended way to get bacteria off your hands?
Government of Canada and the Centers for Disease Control and Prevention recommends using
soap and water
to remove germs from your hands.
Controlled variable: Each participant was given the same instructions (method and time spent) on how to wash their hands with each method. Bacteria samples before and after treatment were swabbed in the same way. All agar plates were incubated at 37oC for 24hrs. The amount of soap, hand sanitizer and number of wipes used were all the same. The percent alcohol was the same between hand sanitizers.
Manipulated variable: The different treatments participants used to washed their hands. The variables were water, soap and water, hand sanitizer, expired hand sanitizer and sanitizing wipes. Time was also manipulated when using soap and water (10 or 20 seconds). Participants also dried their hands with either paper towel or air dried them.
Responding variable: Quantity of bacteria.
Four participants in the child group (ages between 6 and 13 years old) and two participants in the adult group (ages 18 and over) volunteered for the research study. The child participants were labeled as A, B, C and E. The adult participants were labeled D and F. Each participant signed an informed consent form 2C and the study was approved by the Calgary Youth Science Fair ethics committee.
All participants were asked to “play” for 30 minutes to load their hands with bacteria. They were then swabbed with DPBS to obtain the “before” bacteria count. They were then instructed to wash their hands with the different hand washing protocols. After their hands were completely dry they were swabbed again for their “after” bacteria count. This procedure repeated until all treatment protocols were completed.
Participants were asked to wet their hands for 15 seconds under running water while scrubbing their hands. They either dried their hands on a clean square of paper towel or air dried their hands depending on the protocol used.
Soap and Water Protocol
Participants were asked to wet their hands for 5 seconds and put 1 pump of soap on their hands. Water was turned off. They were instructed to scrub between their fingers, palms, fingertips and backs of their hands for either 10 or 20 seconds depending on which protocol was used. Then they would rinse for 15 seconds and dry on a clean square of paper towel or air dry depending on the protocol used.
Participants had half a teaspoon of sanitizer dispensed on their hands. Then they were instructed to scrub between the fingers, the tips of their fingers, palms and backs of hands. They would scrub for 15 seconds and let their hands air dry until completely dry.
Hand wipe protocol
Participants were given 1 new hand wipe each, and instructed to wipe each finger, palms, between fingers and backs of hands for 15 seconds. Then they would let their hands air dry until completely dry.
To ensure bacteria was not introduced while swabbing, a cloth mask and a pair of gloves were worn. One sterile cotton swab was dipped in sterile DPBS. Participants were swabbed before and after treatment. Their fingertips, palms (swabbed in an “X”), in between fingers and knuckles were all swabbed. The cotton swab was streaked onto an LB agar plate in a “Z” pattern. To ensure all materials were sterile and there was no bacteria introduced a negative control of DPBS was streaked on an LB agar plate. To ensure that the agar plates could support bacterial growth, positive controls were streaked on LB agar plates. The positive control for experimet 1 was the bottom of school shoes, experiment 2 bottom of boots and experiment 3 was the inside of participant E’s mouth.
Incubation and Bacterial Counting
After swabbing the participants, the LB agar plates were incubated at 37oC for 24 hours. The plates were taken out of the incubator and were counted. Each colony was counted and put into a table.
- All participants colonies increased in bacterial count for water only
- Participants B and C’s colonies increased while participant A’s colonies decreased for soap and water 10 seconds
- Participants B and C’s colonies increased while participant A’s colonies decreased for soap and water 20 seconds
- All participants colonies decreased in bacterial count for sanitizer
- Participants didn’t have enough bacteria before treatment on expired hand sanitizer
- All participants colonies decreased in bacterial count for sanitizing hand wipes
- Participants A and B’s colonies decreased while participant C’s colonies increased for water only
- Participants A and C’s colonies decreased while participant B’s colonies increased for soap and water 10 seconds
- Participants A and C’s colonies decreased while participant B’s colonies increased for soap and water 20 seconds
- All participants colonies decreased for expired hand sanitizer
- I looked at the additional controls and none of the sources I thought were giving off bacteria (paper towel, soap and water) to make soap and water go up in bacterial count
- All participants colonies decreased for water only
- All participants colonies decreased for soap and water 10 seconds
- All participants colonies decreased for soap and water 20 seconds
- All participants colonies decreased for hand sanitizer
- All participants colonies decreased for expired hand sanitizer
- All participants colonies decreased for sanitizing hand wipes
The results from soap and water were surprising because the number of bacteria on all of the participant hands increased which goes against government recommendations. To rule out the possibility that the water was giving off bacteria or the paper towel, I need to streak them out on an LB agar plate. I would also ask participants to air dry their hands just like they do for the hand sanitizer and wipe protocol.
All participants in the expired hand sanitizer group did not have enough bacteria before treatment to see if the expired hand sanitizer worked. This treatment group would have to be repeated.
Participants B and C are my youngest participants and their colonies are still inconsistent with most treatments.
Maybe younger participants don’t listen as well or cooperate so I have decided to add adults to my study.
The results were much more consistant than the previous experiments. I still saw the most reduction when an alcohol based hand sanitizer was used.
From all 3 experiments the alcohol hand sanitizers were the most consistent in reducing bacteria on hands. Although the most recommended way to clean your hands according to the CDC and the Government of Canada is to use hand soap and water for 20 seconds, it produced the most variable results in my study. This variability might be due to the age of the participants. Perhaps younger participants don’t cooperate or listen to instructions as consistently as an older child or adult. In the end my hypothesis was not supported by the data in this experiment. Maybe the best way to wash your hands is to use soap and water to remove visible dirt and then follow with an alcohol hand sanitizer to remove the remaining bacteria that was missed by the soap and water.
Based on my data, the ranking for the best way to remove bacteria from your hands is (list from best to worst): hand sanitizer, hand sanitizing wipes, 20 second soap and water, 10 second soap and water and water only.
- Try washing hands first with soap and water for 20 seconds and then use hand sanitizer immediately
- Have a larger participant group with both children and adults
- Does it matter what type of soap you use (eg./ bar soap, liquid soap, foaming soap)
- Determine which antibacterial hand wipe is the most effective (eg./ different brands)
- Does the scent matter for removing bacteria with hand sanitizer
- Does the kind of hand sanitizer matter for removing bacteria (eg./ non-alcohol sanitizer, different percentages of alcohol)
Sources Of Error
1. Participants not washing hands correctly or doing it the wrong way
2. Participants not listening as well as I thought
3. Inconsistant swabbing
Principles of Microbiology, Ronald M. Atlas, 1995.
Jane Lee Jia Jing , Thong Pei Yi, , Rajendran J. C. Bose, Jason R. McCarthy, Nagendran Tharmalingam and Thiagarajan Madheswaran. 2020. Hand Sanitizers: A Review on Formulation Aspects, Adverse Effects, and Regulations. International Journal of Environmental Research and Public Health. 17: 3326.
Dixit A, Pandey P, Mahajan R, and Dhasmana DC. 2014. Alcohol Based Hand Sanitizers: Assurance and Apprehensions Revisited. Res. J. Pharm. Biol. Chem. Sci. 5, 558–563.
I would like to thank Dr. David Proud and his laboratory at the University of Calgary for supplying all of my sterile materials such as the LB agar plates, sterile cotton swabs and sterile DPBS.