| Does Antibacterial
Hand Soap Kill More Bacteria Than Non-Antibacterial Hand Soap? |
Researched by Jennifer W.
2003-04 |
|
PURPOSE
The purpose of this experiment was to determine if antibacterial hand
soaps are more effective at killing bacteria than non-antibacterial hand
soaps.
I became interested in this idea because microscopic life has fascinated
me for a long time and I am concerned about human health and disease.
The information gained from this experiment would help large institutions
such as hospitals, schools, and homemakers, if there is no difference people
will want to know this so they dont spend extra money or time on getting
antibacterial hand soaps.
HYPOTHESIS
My hypothesis was that there would be no difference between antibacterial
hand soaps and non-antibacterial hand soaps on killing bacteria.
I based my hypothesis on a statement made by Elaine Larson, a professor
at Columbia University School of Nursing, after studying whether it matters
if the hand soap is antibacterial or not on killing germs. There wasnt
any difference in the bacteria counts on the hands between those who used
the antibacterial or the plain soap.
EXPERIMENT DESIGN
The constants in this study were:
* The amount of Antibacterial hand soap
* The amount of non-Antibacterial hand soap
* The amount of bacteria put on the agar plates
* The temperature of incubator
* The way the bacteria are applied to the agar plates.
* The way you grow the bacteria.
* The size of the agar plate.
* The way the soap discs are applied to the plates.
* The way the bacteria are measured.
The manipulated variable was the antibacterial hand soaps and the non-antibacterial
hand soaps.
The responding variable was the amount of bacteria killed.
To measure the responding variable I will measure the death zone diameter
of the bacteria with a caliper ruler.
MATERIALS
| Quantity |
ITEM DESCRIPTION |
| 3 |
Swab |
| 6 |
Pipette |
| 3 |
agar plates |
| 1 |
Caliper ruler |
| 3 |
Antibacterial hand soap |
| 3 |
Non-antibacterial hand soap |
| 9 |
Test tube |
| 18 |
Soap discs |
| 10 |
Milliliters of soap |
| 1 |
Incubator |
PROCEDURES
1. The microbiologist isolates and grows a strand of three different
bacterial cultures.
a. Escherichia coli
b. Staphylococcus aureus
c. Staphylococcus epidermidis
2. Mix the selected colony type in sterile salt water. Adjust the suspension
to a .5 McFarland turbidity visually.
3. Soak a sterile swab within 15 minutes of adjusting the suspension.
Rotate swab several times, pressing firmly on the inside wall of the tube
above the fluid level.
4. Swab the entire surface of the Mueller ?Hinter agar plate three
times, turning the plate 60 degrees between streaking to ensure even distribution.
5. Measure 10 micro liters of soap onto test disks.
6. Dispense the soap discs on the surface of the inoculated plate
7. Invert plate with the lid on and tap gently to be sure that all
the discs stay on the agar surface.
8. Place the inverted plate in 35 degrees Celsius non-CO2 incubator
within 15 minutes of disc application.
9. Incubate plates for about a day.
10. Examine the plate a few inches above a black nonreflecting background
with reflecting light. Measure the diameter of complete inhibition as detected
by the unaided eye. The caliper ruler is used to measure the diameter of
the death zone of the bacteria in millimeters.
11. After all the bacteria tests have been done, kill all the bacteria
you have worked with. They should be autoclaved using the standard hospital
procedures.
RESULTS
The original purpose of this experiment was to determine if antibacterial
hand soaps are more effective at killing bacteria than non-antibacterial
hand soaps.
The results of the experiment were that antibacterial hand soaps work
better at killing bacteria. On average the zone of death was
51 millimeters for antibacterial but only 22 millimeters for non-antibacterial
hand soaps.
See the table and graph below.
CONCLUSION
My hypothesis was that there would be no difference between antibacterial
hand soaps and non-antibacterial hand soaps on killing bacteria.
The results indicate that this hypothesis should be rejected.
In fact antibacterial hand soap was more than twice as effective.
Because of the results of this experiment, I wonder if these soaps would
have similar results against other species of bacteria. I also wonder
if other soaps on the market would be more effective. It would also
be interesting to test various antiseptics instead of soaps.
If I were to conduct this project again I would do more then one trial
for each soap/bacteria combination. Also I would use more kinds of
soap.
Research Report
Introduction
Bacteria can cause infections and diseases. Thats why washing
your hands is so important. Knowing whether Antibacterial hand soaps
work better at killing bacteria than Non-antibacterial hand soaps is important
for people concerned about health.
Bacteria
Bacteria are simple organisms that consist of one cell. They are one
of the smallest living things. Bacteria are classified as prokaryotes.
There are many types of bacteria that live anywhere. Most bacteria
are harmless to humans, but some can cause diseases.
Bacteria live on the skin and in the mouth, intestines, and breathing
passages. They can enter the body through the natural openings such
as the nose and mouth, also through breaks in the skin. If they do
enter the body they can destroy healthy cells and cause infections.
Disinfectants and antiseptics can kill bacteria.
E. coli
There are a variety of E. coli bacteria present in nature. They are
found in the intestines of healthy humans and healthy animals. E. coli
can be spread from one person to another, this happens most often when
an infected person doesnt wash his or her hands properly.
Staph
The full name for staph is staphylococcus. There are many types of staph
such as staph aureus and staph epidermidis. Staph is gram-positive
spherical bacteria that occur in microscopic clusters resembling grapes.
Aureus and epidermidis are significant in their interactions with humans.
Aureus colonizes mainly in the nasal passages, and epidermidis is an occupant
of the skin. They can cause many infections such as food poisoning
and toxic shock syndrome. Washing your hands properly is the
most important way to prevent staph.
Antibacterial and Non-antibacterial hand soaps
Regular soap decreases waters surface tension and binds to dirt, oil
and bacteria. Antibacterial hand soaps can kill more bacteria but
it takes about two minutes for it the soap to start working, by then it
has probably been washed off your hand. Also antibacterial hand soaps can
kill bacteria that can actually benefit us. It is best if young children
do not use antibacterial hand soaps because the need to interact with the
germs to train their immune system. If they do not interact with
some of these germs it will make them more likely to develop asthma or
other immune-system diseases.
Summary
There are many types of Bacteria. Although some are harmless,
others can cause infections and diseases. Many bacteria live on your
skin. Thats why washing your hands is so important. Antibacterial
hand soaps are intended to kill bacteria. Knowing whether they are effective
is important for people concerned about health.
|
| BIBLIOGRAPHY
Bacteria. Microsoft Encarta. 2001 edition. CD-ROM. Redmond,
WA; Microsoft Corporation, 2001.
Clark, Marie. Personal interview. December 8, 2003.
Greene, Alan. Antibacterial hand soaps. December 10, 2003 http://www.drgreene.com/21_819.html
Metcalf, Eric Antibacterial Soaps, Bursting the Bubble May 2003.
Schlessinger, David Bacteria, The World Book Encyclopedia, 1999.
|
ACKNOWLEDGEMENTS
I would like to thank the following people for helping make my project
possible:
* Mr. Newkirk for helping me with my experiment.
* Mrs. Helms for answering any questions I had.
* My parents for transporting me to and from the hospital to do my
experiment.
* Marie Clark for helping me conduct my experiment at Memorial Hospital and supervising me.
Top of page
Menu of 2003-2004 Science Projects
Back to the Selah Homepage
|
