Antibacterial Hand Sanitizers: Hype or Help?

Lately, it seems that people have become more conscious of cleanliness. And in response, many soaps and cleansers claim to be antibacterial. Is it true? Steven Paletz wondered whether ethanol is the only effective waterless antibacterial agent and decided to check it out.

Project display for “Anti-bacterial hand sanitizers: Hype or help?”

Hypothesis

I believe that waterless hand sanitizers and generic ethanol are equally effective in killing bacteria. I also believe that AloeGuard, which contains chloroxylenol, will be just as effective as ethanol products, because it is used in hospitals.

Independent variables

Antibacterial cleaners

Dependent variables

Number of bacteria colonies

Controls

• Bacteria tested
• Incubation type and period
• Measurement methods

Experimental groups

• Purell
• AloeGuard
• Alcare Plus
• Bath & Body Works antibacterial hand sanitizer
• 62 percent solution of ethyl alcohol
• 6.2 percent solution of ethyl alcohol

Control groups

No cleaner used

Materials

• One 8 oz. bottle of Purell waterless hand sanitizer with aloe
• One 8 oz. bottle of Bath & Body Works waterless hand sanitizer
• One 9 oz. can of Alcare Plus waterless hand wash foam
• One 4 oz. bottle of AloeGuard waterless hand cleansing lotion
• 40 petri dishes with nutrient agar (a seaweed product used as a medium for growing cultures)
• Ethyl alcohol
• Rotating plate
• Bunsen burner
• Glass rod
• XL1 blue strain of E. coli bacteria
• 40 test tubes
• Eyedropper
• Vortex
• Incubator
• Gloves
• Distilled water
• Tape
• Pipette

Procedures

1. Put on gloves and other protection.
2. Dilute the different hand sanitizers in the bacteria (using the testing tube) as follows:
   • For the 1:1 dilution, 100 ml of bacteria to 100 ml of the cleanser
   • For the 2:1 dilution, 50 ml of bacteria to 100 ml of the cleanser
3. Shake the tubes that contain bacteria and hand sanitizers and let them sit for 15 minutes.
4. Place 50 ml of each dilution onto a petri dish.
5. Place the bacteria in the incubator for 24 hours at 37@dgs Celsius.
6. After incubation period, count the bacteria colonies and record the results.
7. Seal the petri dishes with tape and dispose of them properly.
8. Repeat for trials 2 and 3.

Results

The table shows the number of colonies remaining after 24 hours, for both the 1:1 and the 2:1 concentration of each antibacterial.

Table             Bacteria Remaining after Application of Test Substances for Each Trial

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