The Effect of Antiseptics on the Survival Rate of Different Types of Bacteria

Researched by Zach F.


The purpose of this experiment was to determine the effect of different antiseptics on the survival rate of bacteria.

I became interested in this idea because I was really fascinated with microbiology and how you get a sore throat or get sick and how you could help stop it.

The information gained from this experiment would help a lot of people like doctors, nurses, other heath professionals, and patients.


My hypothesis was that Clorox bleach would kill the most bacteria.

I based my hypothesis on a statement by Marie Clark a microbiologist. She told me, “In all my experience, I found that bleach works the best to kill bacteria. ”

Back to Top


The constants in this study were: 

  •  The types of bacteria
  • Testing Procedures
  • The amount of antiseptics added
  • The environment 
  • The types of antiseptics
  • The agar plates 

The manipulated variable was the type of antiseptic.

The responding variable was the diameter of the area where the bacteria didn’t grow.  

To measure the responding variable I will use a special ruler called a caliper.

Back to Top


 100ul  Chlorine Bleach
100ul  Alcohol (Isopropyl) 70%
100ul Providone Iodine 10%
100ul Chlorhexidine 4%
100ul Saline Solution 0. 45%
Blood agar plate
Lots Swabs
1 Forceps/Tweezers 
1 Lab coat
 1 Pipette 10ml
Lots Disposable Pipette Tips
Back to Top


1. First gather the bacteria.

 a. Escherichia coli 
 b. Staphylococcus Aureis
 c. Pseudomonas Aerugines 
 d. Staphylococcus Epidermidis
2. Then gather the antiseptics.
a. Chlorine Bleach
b. Alcohol (Isopropyl) 70%
c. Proidone Iodine 10%
d. Chlorhexidine 4%
e. Control- saline solution 0. 45%
3. Next punch tiny discs out of filter paper. Five discs for each antiseptic.
4. Soak the discs in the antiseptic solution
a. Each disc 20 Micro liters
5. Then check the density of solution with bacteria. Density has to be 15%. Use a colorimeter to find 15%. Swab the bacteria on blood agar plates.
6. Next place the discs on the blood agar plate.
a. Make sure discs are pretty far apart.
7. Leave blood agar plates in an incubator for 24-48 hours.
8. After the time check the plates and measure the diameter of the zone if death using a caliper. Write down your result.
9. Destroy the remaining bacteria with an autoclave using the hospital’s procedures.
Back to Top


The original purpose of this experiment was to determine the effect of different antiseptics on the survival rate of bacteria.

The results of the experiment were that Clorox bleach did the best and had the biggest zone of death, for every bacteria type, averaging 46mm. in diameter. Chlorhexidine 4% did the second best overall and had a zone of death, averaging 27mm. Proidone Iodine 10% had a smaller zone of death, 16. 5 on average. Control-saline solution 0. 45% only worked on Staphyloccus Epidermidisso the average was less than 4mm. Alcohol (Isopropyl) 70% did the worst and did not kill any bacteria.  

See my table and graph.  

Back to Top


My hypothesis was that Clorox bleach would kill the most bacteria.  

The results indicate that this hypothesis should be accepted, because for every type of bacteria, bleach had by far the largest zone of death.

Because of the results of this experiment, I wonder if other types of bacteria were tested would bleach still do the best. Maybe if I had used other antiseptics, bleach might not have been the best.

If I were to conduct this project again I would have done my experiment twice or three times instead of once to make sure my results were constant. It was surprising that saline killed any bacteria at all. It was also unexpected for isopropyl alcohol to be completely ineffective. More trials might help clear this up.

Back to Top


Finding out which antiseptics are most effective is very important. Without good health people could not do many important things like going to school or to work. It would be hard to live a normal life if you got a terrible sickness or disease. That is why finding out which antiseptics help you best is very important.

Bacteria are different types of germs. There are thousands of types in many different shapes. Here are some bacteria and what they look like. There is cocci which look round or oval. Bacilli which look like a rod, vibria which look like commas and spirilla which look like spirals.  

Bacteria use binary fission to reproduce. This is a process where bacteria split into two different parts. This process can happen about every 20 minutes. If the bacteria is a survivor of some antibiotic, when it splits the new bacteria will be invulnerable to that antibiotic. This is how bacteria become resistant to antibacterial medicines.  

Helpful Bacteria
Lots of bacteria can actually help inside your body. There are bacteria on your teeth and in your stomach. The ones that are on your teeth help break down food in your mouth. The bacteria in your stomach can help by decomposing and digesting food.

Harmful Bacteria
There are many types of bacteria that are very harmful and cause diseases such as cholera, gonorrhea, leprosy, syphilis, tuberculosis, typhoid fever, and whooping cough. All of these diseases are very harmful to your body. Some types of harmful bacteria can get into your body and stop it from functioning right by killing healthy cells. Botulism can cause deadly food poisoning in improperly canned food. If your resistance to disease is low your body can get infected. Even some bacteria that normally help can also hurt you. The bacteria on your teeth make a sugar toxin. After a while if you don’t brush your teeth carefully they can cause tooth decay. There is a type of bacteria called Staphylococcus. These bacteria are commen skin infections but are harmless to most peoples skin. If the bacteria is trapped in your skin from sweat they can cause infections like pustules, boils, abscesses, sties, or carbuncles.  

Antiseptics are substances that kill bacteria. They are used for many things and help people a lot. Surgeons use antiseptics to spray on their equipment and the wound. Some eye drops and mouth washes are antiseptics.   Alcohol that you put on your cuts and scratches is an antiseptic.   Iodine is an antiseptic. In the doctors office they rub alcohol on your arm before you get a shot too.

Antiseptics are made to be harmless to your skin, unlike disinfectants that can burn and irritate your skin. They can be used more places without harming you. Antiseptics are made for all sorts of things that antibiotics can’t do. They are made for irritated eyes and cuts, even for surgery when there is an incision.  

Antiseptics and Bacteria
Antiseptics are made to kill bacteria. When you get a cut, bacteria gets in. Put antiseptic on it to kill the bacteria and stop the cut from being infected. The antiseptic goes into the cut and will kill the bacteria before it spreads and starts an infection. If you don’t put medicine on the cut the bacteria could make the cut infected. Some antiseptics are made to kill different types of bacteria. Some antiseptics are made stronger than others. Some types of bacteria no antiseptic can kill. It is very important to know which antiseptics work best on specific bacteria.  

It is very important to find out which antiseptic works the best against different types of bacteria to protect health. Antiseptics help us get better sooner and stay healthier. If you weren’t healthy it would be hard to be happy and productive.  

 Back to Top

“Antiseptics and Disinfectants. ” Stack of Lists. September 1, 1994.

“Bacteria(singular bacterium). ” The Hutchinson Dictionary of Science. October 29,2003.

Clark, Marie. Personal Interview. December 29, 2003.

Clayman, Charles. “Alcohol Rubbing. ” The American Medical Association Encyclopedia of Medicine, 1983

Clayman, Charles. “Antiseptics. ” The American Medical Association Encyclopedia of Medicine,1989

“Microbiology. ” Britannica Intermediate Encyclopedia. December 9, 2002

“Peroxide. ” Microsoft Encarta Encyclopedia Deluxe. 2001

Rodowskas, Christopher. "Antiseptics," World Book Encyclopedia,  2001.

Schlessinger, David. “Bacteria,” World Book Encyclopedia, 2002

Schiff, Lisa. “CDC: Alcohol-Based Hand rubs are better than soap and water. ” News Watch: Professional Update. January, 2003: 1

 Back to Top


I would like to thank the following people for helping make my project possible:

  •  My parents for always supporting me and taking me to the hospital to do my experiment.
  • Mr. Newkirk for correcting my report and helping me with my graph.
  • Mrs. Helms for helping me figure out things that I did not know.
  • Marie Clark for taking time out of her busy schedule to help me with my experiment.  
  • My sister, Rachel, for helping me figure out what to do my experiment on.  


Top of page

Menu of 2003-2004 Science Projects

Back to the Selah Homepage