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Access Excellence Classic Collection
Handwashing Laboratory Activities
by: Christine L. Case, Ed.D.,
Microbiology Professor at Skyline College
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| photographs by C.L Case Ed.D
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Materials
These materials are for each pair of students.
- Two petri plates containing nutrient agar
- Soap
Procedure
- 1. Divide two nutrient agar plates into four quadrants.
- a. Label the quadrants of each plate 1 through 4.
- b. Label one plate "Water," the other "Soap."
- 2. One student use the "Water" plate.
- a. Touch section 1 with your fingers.
- b. Wash well without soap.
- c. Shake off excess water and while still wet touch section 2.
- 3. Do not dry your fingers with a towel.
- a. Wash again and while wet touch section 3.
- 4. Wash a final time and touch section 4.
- 5. Another student should use the plate labeled "Soap."
Repeat the procedure step 2 (Except 2b. Wash with soap) through 4.
- 6. Incubate the plates inverted at 35C or room temperature until the next period. (Usually 24 hours at 35C or 48 hours at room temperature.)
- 7. Record your results:
- a. 4+ = maximum growth
- b. 3+ = moderate growth
- c. 2+ = some growth
- d. 1+ = a little growth
- e. neg = no growth
Materials
These materials are for the whole class.
- Two sterilized bowls (wash then rinse out with alcohol and sterile water)
- 100 ml sterile water per bowl
- Two petri plates containing nutrient agar
Procedure
- 1. Label one nutrient agar plate "Not washed," the other "Washed."
- 2. Go to the restroom and touch all the things you would normally touch, such as doors and faucets, but do not wash your hands.
- 3. Immerse your hands up to mid-palm in 100 ml sterile water. Rub your fingers against each other.
- 4. After everyone has rinsed their hands in the same container of sterile water, transfer 0.5 ml of the wash water from step 2 to the surface of the "Not washed" plate. Spread the inoculum over the plate with an L-shaped glass rod. (The rod can be sterilized by dipping in alcohol and washing off the alcohol with sterile water.)
- 5. Go to the restroom and touch all the things you would normally touch then wash your hands.
- 6. Immerse your hands up to mid-palm in 100 ml sterile water. Rub your
fingers against each other.
- 7. After everyone has rinsed their hands in the water, transfer 0.5 ml of
the wash water from step 5 to the surface of the "Washed" plate. Spread the inoculum over the plate with a sterilized glass rod.
- 8. Incubate the plates inverted at 35C or room temperature until the next
period. (Usually 24 hours at 35C or 48 hours at room temperature.)
- 9. Record your results:
- a. 4+ = maximum growth
- b. 3+ = moderate growth
- c 2+ = some growth
- d. 1+ = a little growth
- e. neg = no growth
Options
Compare hot/cold water; bar/liquid soap; dispenser types, e.g., bar soap, pump bottle, slit top, powdered soap; soap ingredients, e.g., alcohol, soap, detergent, hexachlorophene, medicated soaps.
Questions
- Why is it not necessary and, in fact, undesirable to remove all bacteria from the skin?
- The microorganisms that are normally present on the human skin are not pathogens. Why does a surgeon scrub for 2 to 5 minutes with an antiseptic soap before operating?
- List some diseases that can be transmitted on hands.
- Make a sign for your school restroom that will get students to wash their hands. Make a sign for your school that will encourage students who own lizards to wash their hands after handling the lizard.
For further information please see:
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