Names __________________ ____________________ Class ______ Date ____
_______________________ ______________________
Fun with Fomites
We’ve all read the story about Horton and have heard of Whoville. But have you
ever wondered if such an existence was possible or how and where small “Who’s”
could live? It might be time to find out but let me warn you, the creatures you may
discover are not that cute and they don’t sing songs!
It’s that time of year when we all wonder, if our hands are clean and are the surfaces we touch clean! You may
soon find out if you need to wash more often! All you have to do is look on a fomite!
What is a fomite? Fomite is a term for any inanimate object that can carry disease-causing organisms. Your
textbook, door knobs, a classroom stapler, 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, water fountains, refrigerators, 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 diseasecausing. 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.
Note: This is an activity that you do with a group and will work on for several days.
Materials:
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One sterile Petri plates prepared with nutrient agar
Sterile cotton swabs
Vial of distilled water
Paper towels
Cellophane tape
Permanent marker or grease pencil
For the last day: a disinfectant such as 70% alcohol solution (mix 7 parts alcohol to 3 parts water), 10%
bleach solution (mix 1 part bleach to 9 parts water), liquid soap, Lysol® or other household cleanser.
Procedure:
1.
If you have long hair, tie it back to keep it from dangling into the Petri plates as you’re working. Wash
your hands. Clean your work area by dabbing, not pouring, disinfectant solution onto a paper towel and
swabbing your area. Set out your Petri plate but DO NOT OPEN THE PLATE UNTIL YOU ARE ASKED
TO DO SO.
2. Take one unopened Petri plate and using a marker, divide the bottom of the plate into four
equal sections like the diagram to the right. Each person will swab a section. Number each
section 1-4 starting in the upper right and working clockwise. Then write your initials and
your partner’s initials by the number of the section that he/she will swab on the SIDE or edge of the
bottom plate.
3. Choose your FOMITE…The fomite could be an object in the school like a
doorknob, lab counter, water fountain, toilet seat, bathroom sink, wrestling
mat, etc. Your partner will choose a fomite as well.
4. Write in your chosen fomites and write them below. Be sure to get them approved.
Fomite 1 _________________
Fomite 2 ___________________
Fomite 3 _________________
Fomite 4 ___________________
5. To help you keep track, write the initials of the person who swabbed that particular quadrant on the
SIDE or edge of the bottom plate.
6. IF you are going to a known “germy” area, put one glove on your main hand. (the one you write with) or at
least wash your hands after you swab. Don’t touch anything but the swab with this gloved hand!!!! (throw
glove away)
7. Go to your FOMITE…FOLLOW THE DIRECTIONS CAREFULLY!
8. Select a cotton swab and be careful not to touch the tip. Dip the swab into the distilled water and then
swab your chosen object with all sides of the swab tip by turning and twisting the swab as you move it
across the object’s surface.
9. Now open the lid of the plate and GENTLY make your streaks firm
but do not gouge! Be sure to make your streaks in the section that
you swabbed!
10. Use firm, but GENTLE pressure and do not retrace your previous
streaks. Your streaks should make only very slight impressions in the agar—don’t gouge. Close the plate
and seal it shut with two pieces of tape placed along the side—don’t cover over the top with tape or you
won’t be able to see the inside of it well.
11. Dump your left-over water in the sink and throw your cup and swabs away.
12. Return to class, tape your dish shut by placing a small piece of tape on each side of the dish. Make your
first observation (details below) and then place your plates on the tray in the front of the room. Wash
your hands.
a.
Using your data and observations sheet, write an observation of your dish. Today is Day 1. Draw
and write about every detail, like bubbles or specks that you see in the nutrient. You will need to
be VERY observant and notice ANY changes over the next few days so start out doing your best!
DATA: Fomite Observations (one per group)
Daily written and visual observations of what you see in your Petri dish. Include shapes, colors, measurements
(mm or cm). Do NOT open your dish! Be careful and do not drop it!
Written Observation Day # _____ (just after you swab)
Date: _________________________
___________________________________________
Visual Observation
___________________________________________
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Written Observation Day # ___________
Date: _________________________
Visual
Observation
_________________________________________
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Written Observation Day # ___________
Date: _________________________
Visual Observation
Written Observation Day # ___________
Date: _________________________
_________________________________________
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Name _____________________________ Class______ Date ____
Conclusion
(one per person)
Questions to answer after your last observation.
1. Compare your plate to the Control Plate. Which plate grew the most
and biggest colonies? Why do you think that is?
2. Do you see a pattern in the size and amount of colonies in each plate? Explain.
3. Which FOMITE grew more microbes? Why do you think that happened?
4. Look at one or more of your microbes under the microscope. Leave the lid on your
petri dish. Draw one of the microbes below.
5. How do we control microbial contamination in our homes and schools?
6. Look up and read about one or more of your microbes on the website below.
(http://www.microbeworld.org/microbes/) What microbe do you think you have?
7. Write a paragraph that summarizes what you learned about your microbe/s.
8. How would your microbe fit into the world of living things? Explain below or on the
back. http://www.kidsbiology.com/biology_basics/classification/classification1.php