Abstract
Germs are everywhere! We try and clean our home with disinfectants, but do we really get rid of all the germs? Find out with this "hands-on" experiment.Objective
In this experiment you will test several disinfectants to see which ones work best to decontaminate the surface of a cutting board.
Introduction
When your mom tells you to wash your hands before dinner, she is thinking about all the germs you might have on your hands from touching the world around you. Germs are everywhere! Germs, or microorganisms, that cause illness and disease can grow on many surfaces called fomites. Here is a good description of fomites and how they harbor germs from the American Society for Microbiology:
"Fomites? What are fomites? This is a term for any inanimate object that can carry disease-causing organisms. Your cutting board, kitchen sink, the change in your pocket and even that pen you keep putting in your mouth are all fomites. Very few things we encounter in our everyday activities are sterile, or microbe-free, including us. At birth, microbes immediately begin colonizing our bodies as they do most every object in the world. They float around until they come in contact with a surface that offers food and shelter. You are most likely to find microbes in and on dark, moist objects that frequently come into contact with food, dirt or vegetation. Bathroom surfaces, hairbrushes, refrigerators, kitchen sinks and cutting boards often have lots of microbes on them. But doorknobs and walls have fewer because they are nutrient-poor and dry.
"Most of the microbes on our bodies and other surfaces are harmless, but some are pathogenic or disease-causing. For this reason, we want to control the number of microbes around us. The odds of becoming infected increase with the number of microbes on surrounding objects. But what can we do to affect the number of microbes on surfaces around us?
"In this activity, you will test a chosen fomite for the presence of microbes and the effects of a disinfectant by growing colonies of bacteria in a medium on petri plates. A medium has food, vitamins and salts that help microbes grow. You usually don’t see bacterial colonies like those that form on petri plates on everyday surfaces. That’s because there is rarely such a perfect concentration of nutrients on fomites in nature." (ASM, 2001)
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| An agar plate showing colonies of microorganisms that have been isolated from a deep-water sponge. (Wikipedia contributors, 2006; original source of image from NOAA Ocean Explorer) |
How well do disinfectants work to clean surface bacteria? In this experiment you will use a cutting board as a fomite and test the use of different brands of disinfectants. By culturing bacteria from the surface after you have cleaned it, you will find out how well the disinfectant worked. Which disinfectants will work the best?
Terms, Concepts and Questions to Start Background Research
To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!
Bibliography
Materials and Equipment
Experimental Procedure
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| Number | Type of Disinfectant | Number of Colonies | Other Observations |
| 1 | water (control) | ||
| 2 | |||
| 3 | |||
| 4 | |||
| 5 | |||
| 6 |
Variations
Credits
Sara Agee, Ph.D., Science Buddies
Last edit date: 2007-03-22 22:00:00
If you like this project, you might enjoy exploring careers in Microbiology.
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