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How to Disinfect Petri Dishes

Petri dishes are used along with agar to grow organisms like bacteria in a laboratory to identify species, measure bacteria population or conduct other tests. Agars are specially-formulated materials designed to promote the growth of specific target organisms. Sterilizing Petri dishes after use is important to prevent the spread of dangerous microorganisms, like E. coli. There are two safe ways to sterilize these dishes, and you should select your method based on your laboratory's available equipment.

Things You'll Need

Heat-stable biohazard bag
Autoclave
Metal pan
Autoclave indicator tape
Glass container (optional)
Household bleach (optional)

Instructions

Autoclave Method
- 1
  Place the Petri dishes and at least 100 mL of water inside of a heat-stable biohazard bag. Be sure the dishes can be autoclaved without damaging the dishes or the autoclave device.
- 2
  Place the bag in the metal pan and place a 1-inch piece of indicator tape on the bag.
- 3
  Close the autoclave door and allow the device to run until it reaches 250 degrees in the center of the bag for at least 45 minutes. After the run time, allow the materials inside to cool before removing them.
- 4
  Check the indicator tape to be sure the bag was properly autoclaved. The indicator tape will change color, and color changes varies by manufacturer.
- 5
  Remove the metal pan, drain the liquid from the bag and dispose of the bag in a waste receptacle.
Bleach Method
- 6
  Place the Petri dishes in the glass container.
- 7
  Mix one part bleach with four parts water. Make enough of this solution to saturate the Petri dishes and their contents.
- 8
  Pour the bleach mixture over the Petri dishes and soak overnight.
- 9
  Dispose of the Petri dishes in a trash bin and drain the liquid in a sink or other waste liquid receptacle.

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