Method
1.Agar dishes should be refrigerated until used and ALWAYS stored
upside-down. (I.e. lid on the bottom) This keeps condensation that forms on the lid from dropping onto and disturbing the bacteria growing area.
2.Prepare sterilized water by boiling tap water to 100 C for 10 minutes and then let cool to room temperature.
3.When ready to conduct experiment let agar plates come to room temperature for 1 hour before taking samples.
4.Collect bacteria from each location (e.g. toys, doorknob, examination table, countertop) using one swab for each new location. First dip the swab in sterile water. Next, swab the area in a
side-to-side motion. Then, in an x-mas tree shape swab the agar plate with the same swab.
5. Tape all the way around vertically NOT the circumference and label what you swabbed.
6. Repeat step 4 and 5 until you swabbed all the objects, which are the countertop, the examination bed, the doorknob, and the toys. Then, store upside-down at about 37oC but NOT in direct sunlight. Count visually the colonies you can see with the naked eye everyday for 12 days.
7. Choose one object that you swabbed that you think has a lot of bacteria and swab it again with a new clean swab using the technique given in step 8 .For the object that I swabbed I chose the countertop but I suggest swabbing the toys.
8. Pour sterile water in a sterile container. Place the swab in the water and swab the area. Repeat with the same swab.
9. Use the hole puncher to make 10 small circular disks out of paper towels or filter paper.
10. Pour some of the water into an agar plate and then pour it out.
11. Pickup 1 disk with the tweezers and then in a bowl pour 100% bleach. Soak one of the disks in the bleach and then place it in the agar that had sterile water in it. Label the agar 100% bleach and store it upside-down at 37 C.
12. Repeat step 10and 11 but with:
B=bleach W=water
90%B 10%W=9mLs bleach and 1mL water
80%B 20%W=8mLs bleach and 2mLs water
70%B 30%W=7mLs bleach and 3mLs water
60%B 40%W=6mLs bleach and 4mLs water
50%B 50%W=5mLs bleach and 5mLs water
40%B 60%W=4mLs bleach and 6mLs water
30%B 70%W=3mLs bleach and 7mLs water
20%B 80%W=2mLs bleach and 8mLs water
10%B 90%W=1mL bleach and 9mLs water
0%B 100%W=0mLs bleach and 10mLs water
Use sterile syringes to measure the different volumes of bleach and water needed. ASK A PARENT FOR HELP BECAUSE BLEACH IS COROSIVE AND THE FUMES CAN KNOCK YOU OUT.
13. Check agars plates everyday and measure in mm how big the haloes are from the disk and record in a notebook in a table.