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 The Effect of Clorox on the Bacterial Content on Restroom Doorhandles

 The Experimenter

Researched by Sarah S.


The purpose of this experiment was to compare the bacterial content before and after the use of Clorox wipes on the inside and outside door handles of restrooms.

 I became interested in doing a project on bacteria because I am interested in a career in medicine, biology or microbiology. In addition my mom has taught me about avoiding bacteria in restrooms and encouraged me to use a paper towel instead of my hand to open the door when leaving. I thought it would be good to study this scientifically.
The information gained from this experiment affects almost everybody on earth today but it should especially help store and restaurant owners in trying to keep their bathrooms clean. The bacteria on bathroom door handles could possibly cause sickness and disease and needs to be dealt with properly.


My first hypothesis was that there would be more bacteria on the inside of the door handle than the outside due to the germs picked up from the restroom and people not washing their hands. 

My second hypothesis was that there would be more bacteria in supermarket restrooms such as Wal-Mart or Fred Meyer because there are usually more people cycling through.

My third hypothesis was that the Clorox wipes would reduce the amount of bacteria significantly.



The constants in this study were:
∑ Time frame project conducted
∑ Amount of time handles were swabbed
∑ Pressure swab was pressed against handle when collecting bacteria.
∑ Type of swab used
∑ Type of agar
∑ Type of Petri dish
∑ Time incubated
∑ Temperature incubated
∑  Type of incubator
∑ Type of bleach used
∑ Same time to dry
∑ Same time wiped with Clorox

The first manipulated variable was the location of sampling: supermarkets, homes, and restaurants.

The second manipulated variable was whether the sample was collected on the inside or outside of the restroom door.

The third manipulated variable was sampling before and after the use of Clorox.

The responding variable was the amount of bacteria on the door handles.

To measure the responding variable the bacteria colonies were counted.

1 Incubator
18 Sterile swabs
18    Petri dishes
18  Blood agar plates
2 Homes
2  Restaurants
2 Supermarkets
1 Lab coat
1 Container of Clorox wipes
1 Stop watch


1. Go to Hospital Lab and obtain 18 sterile swabs.
2. Go to first destination.
3. Go to bathroom and locate outside doorknob.
4. Take out sterile swab 
5. Collect Bacteria:
a. Rub halfway around doorknob as steadily as possible using even pressure for ten seconds using stopwatch.
b. Try to collect bacteria from entire surface.
6. Label Swab with three items.
a. Place bacteria were collected.
b. Inside or outside of bathroom door.
c. Before or after use of Clorox wipe.
7.  Put swab back in carrying case.
8.  Go inside bathroom.
9.  Repeat steps four through seven.
10.  Take out Clorox wipe.
11.  Scrub down doorknob with Clorox wipe for 15 seconds using stopwatch.
12.  Restart stopwatch
13.  Let knob dry 60 seconds.
14.  Repeat steps four through seven except on opposite side.
15.  Repeat steps two through fourteen at all other destinations.
16.  Go to Hospital Lab.
17.  Put on Lab coat.
18.  Transfer Bacteria from swabs to agar by rubbing in three different directions turning Petri dish 60 degrees each time.
19.   Label Plates (as in step 6)
20.  Repeat step 19 through 20 for all remaining swabs.
21.  Incubate plates for 48 hours in incubator at 35° C.           
22.  Wash hands.
23.  Count the number of colonies. If number is to large divide Petri dish into four sections, count each section and add together.
24.  Record number of colonies.
25.  Repeat steps 23 through 25 on all Petri dishes.
26.  Wash hands
27.  Sterilize Petri dishes by putting them in an autoclave. Incinerate swabs.


The original purpose of this experiment was to see the effect of Clorox wipes on the bacterial content on bathroom doorknobs.

The results of this experiment were that there was about 50% more bacteria on the inside than the outside door handle. The disinfectant wipe reduced it 100%. There was an equal amount of bacteria in restaurants and supermarkets and there was a little less that a quarter more in the homes.
See My Table And Graph


The first original hypothesis was that there would be more bacteria on the inside door handle than the outside. 

The results indicate that my 1st hypothesis should be accepted because there was over twice as much in the inside than the outside.

My second hypothesis was that there would be more bacteria in supermarket restrooms.

My 2nd hypothesis should be rejected because the supermarkets and restaurants had the same amount and the homes had approximately 25% more.

My third hypothesis was that the Clorox wipes would reduce the amount of bacteria significantly.

This hypothesis should be accepted because the Clorox wipes reduced the amount of bacteria 100% for all the trials.

My fourth hypothesis was that the Clorox wipes would not reduce the amount of bacteria entirely.

This hypothesis should be rejected because the Clorox wipes reduced the amount of bacteria 100%.

I realize there was a small flaw in this experiment.  Maybe the bacteria weren’t removed by the Clorox disinfectant itself but instead by the process of rubbing the doorknob with the wipe.  To solve this problem I could have tried using a spray instead of a wipe or towel. This could have solved my problem because I would have known if it was the disinfectant itself or the rubbing. I also could have solved the problem by rubbing with a wipe without disinfectant to see if rubbing alone removed the bacteria.

Because of the results of this experiment, I wonder how much bacteria would be reduced by high heat instead of applying disinfectant.  For example, would a heat gun be an effective tool for killing bacteria on door knobs or other surfaces? 


Bacteria are a very important substance on the earth today. It is our food cycle, nature, body and much more. It can be helpful or harmful and everybody needs to know about it.
Bacteria are microorganisms, some are either helpful but many are harmful. We have many bacteria living in our body, most is helpful but if a harmful bacterium enters our body they can make us sick.  There are so many bacteria in the world it is impossible to find them all. There are 300 or more different kinds of bacteria in our mouth alone.  

Human Health
∑ Almost every part in our body has some type of bacteria in it. Our entire body contains of one quadrillion Bacteria (1015 ). There are about 100 trillion (1014) cells in our body so that means there are 10 times as many bacteria as cells in our body. Most of the bacteria live in the large intestine. There are also bacteria in the:
∑ Small intestine
∑ Nose
∑ Colon
∑ Eyes
∑ Skin
∑ Stomach
∑ Throat
∑ Mouth
 Those are just the main places. There are around 500 to 1000 different types of bacteria in the human body.

Types of Bacteria
Some types of bacteria can cause harmful diseases. But bacteria don’t cause every sickness. An example is that bacteria do not cause a regular sore throat, but strep throat is caused by bacteria. Strep throat is caused by a bacterium called streptococcus. Streptococcus also causes tooth decay. Researchers have found the genes of 9 different breeds in 4 different species of Streptococcus. Streptococcus is a cocci bacterium. Some Cocci bacteria are harmful and some are not. Micrococci are known to be harmful to the skin, they cause boils and sometimes more serious, but are rarely dangerous.

A rod bacteria is also dangerous but not that harmful. A bacillus, which is a rod, is not harmful; it is in soil, spores and sometimes food, but a cueus can cause mild food poisoning, diarrhea or vomiting.

Vibriosis can also cause skin infections, diarrhea, cholera and/or blood infections. Vibrio parahemolyticus causes diarrhea, it is usually harmless unless the bacteria cells that cause diarrhea get out of hand they can cause blood infections and very rarely death. People who are at more risk of vibrio are those who have liver disease, excess iron, blood disorder, AIDS and diabetes. It is found in salt water and is usually caused by eating raw seafood such as oysters or shellfish.  You can’t tell if the seafood has vibrio by looking at it. To decrease the risk, avoid eating raw seafood. Most vibrio infections are on the coastal states and occur during June to October.

The history of microbiology started when Robert Hooke built the microscope in 1660 to study plants. Later Antonio van Leeuwenhoek used the microscopes to look as a drop of rainwater, he found little animals he called “animalcules” or eels. Later we found that they were bacteria.

Disinfectants are very important to the human world today because they are an effective way of killing bacteria.  Everybody used them today to keep there home and clean and healthy. The questions is which one works the best. Test are constantly in process to see which one actually works the best. Clorox, Lysol, Bleach in general are very effective in killing bacteria.

Bacteria and disinfectants are very important to the human world today. It is impossible to live without bacteria.  Disinfectants keep the human earth a healthier place to be, there are less sicknesses and diseases because we now know how to control bacteria and we have effective disinfectants.

Alvin, Dr. Monerans and Prostists. Canada: Fizhenry and Robert Silverstien, 1996.

"Bacteria,” World Book Encyclopedia, 1997.

Dennis, Cornia “Bacteria” 10/20/04

Ernst, Rachel. “The Effect of Temperature on The Bacterial Growth Rate.” 10/20/04. <>.

Fracklem, Howard and Margery. Bacteria. Canada: Fizhenry and White side Ltd, 1994.

Finlay, Brett “Bacteria are every ware” January 26, 2005
Garza, Marisol. “Bacterial Content of Water Bottles.” October 20 20 04 <>.

Hamilton, Garry “Why we need germs.” The Ecologist June 1, 2001 pages. 1-12

Jones, Mary. “Bacteria and the Carbon Cycle.” The Hutchinson Encyclopedia of Science September 22, 2003

Smith, Joseph F. “Vibriosis” CHC Library <>

Taylor, Sonia. “Which Waterless Hand Sanitizer is Most Effective in Killing Bacteria.” October 20, 2004. <>.


I would like to thank the following people for helping make my project possible:
  • My parents for driving me to and from the hospital and school.
  • Marie Clark for helping me with my entire project and answering many questions for me.
  •  Mr. Newkirk for helping all the way through and correcting all the mistakes I made.
  • Mrs. Helms for helping me with the colors of my project and working with me on the computer.
  • Rainan for helping me with colors and my presentation.


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