Handwashing Experiment Microbiology

Observation:

Does handwashing alone kill enough bacteria to be effective?

Hypothesis:

Antiseptic sprays are more effective at killing bacteria than handwashing with water alone.

Experiment:

Materials:

5 trays

5 L of sterile water

15 nutrient agar plates

5 sterile brushes

Peppermint hand sanitizing spray

Eppendorf pipette

L-shape Sample Spreader

Beaker containing isopropyl alcohol

Paper towel

Procedure:

Day 1

1. Label the NA plates according to table number, tray number, and dilution. You will then have three NA plates for each of the 5 trays, designated as 0.1mL, 0.2mL, or 0.4mL dilutions.

2. Begin with one volunteer with unwashed hands at Tray 1. Pour one liter of sterile water into the first tray and open one sterile brush. Hand the volunteer the sterile brush and instruct them to scrub their hands in the liter of water for 30 seconds using the brush portion of the scrub brush, not the spongy portion. When completed, allow volunteer to dry hands with one paper towel. Cover tray with aluminum foil until inoculation.

3. Using the peppermint hand sanitizing spray, spray each of the volunteer’s hands twice. Instruct the volunteer to rub hands together until the hand sanitizer has dried.

4. Repeat steps 2 and 3 with Trays 2, 3, 4, and 5, using a new scrub brush and a different liter of water for each tray.

5. Begin the inoculation process. Sterilize the L-shape sample spreader by soaking it in isopropyl alcohol and then flaming off the remaining alcohol.

6. Using the sterilized spreader, mix the one liter of water in Tray 1. Re-sterilize the sample spreader as done previously.

7. Using the Eppendorf pipette, transfer 0.1mL, 0.2mL, and 0.4mL of sample into the appropriately marked NA plates. Spread the samples evenly on their plates using the sample spreader. Sterilize the spreader and allow the samples to soak into the agar plates.

8. Repeat steps 6 and 7 for Trays 2, 3, 4, and 5.

9. Incubate the NA plates at 37°C for 48...