I had conducted some disc diffusion tests with E.coli and S.epidermidis.

Now, I wanna dispose these petri dishes and was wondering the correct way to do it. Many websites mention adding bleach to the agar and disposing them in biohazardous waste bags right away.

I've decided to do the same. But, the lid for all the petri dishes I have are very loose. If I simply dispose the petri dishes in waste bags, I think that the lids are gonna come off and the bacteria may infect the waste bags.

Should I seal the petri dish with some tape like a parafilm so the lids won't come off or is it not a problem that the bacteria may come out onto the waste bags?

(No websites mention the issue of loose lids while disposing, so I wonder if this is a problem at all)

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    $\begingroup$ You don't have an autoclave available? $\endgroup$
    – Chris
    Jul 17 at 12:00
  • $\begingroup$ No, I'm not a professional researcher, a high school student. I just did this exp. at home...so I don't have one $\endgroup$
    – ninetysix
    Jul 17 at 12:11

Autoclave is standard, but bleach can be used. In your case, you'll want all the culture media and dish surfaces to have contact with the diluted bleach solution. I would prepare diluted liquid bleach as described in the link below and pour some in a plastic wash tub to a depth where you can put all your petri dishes etc in and have them fully submerged. Let them sit for at least 30 minutes in the solution, then recover the solids and put them in trash, and dispose of the bleach solution with MUCH dilution down the toilet. Pay attention to the safety suggestions and warnings in the link!

This U of Toronto web page has good info on disinfecting using bleach.


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