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Equipment for correct sterilisation?

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Equipment for correct sterilisation?

Postby Alvino » Tue Sep 11, 2007 8:18 pm

Hi, Id like to first of all say that I'm a "noob" to the site so please be gentle!!

However I've been travelling the internet for a definitive answer to a question that's has been annoying me for some time.

This concerns sterilisation & bloodborn bacteria/spores. I'll come clean (no pun intended!) I've been asked by a friend who is learning to tattoo why an autoclave is required to sterilise equipment. Now I've explained to him that some spores will not be destroyed by boiling as the water doesn't hit the temperature required to kill these "germs". So by using an autoclave you buold up pressures inside that allows the temperatures to reach 130/140c which is needed to kill the spores.

His next question is then why cant I put them in my oven at 150c or use a pressure cooker?

This is where I fall down as I can't give him a definitive answer as to why this is not adequate.

So I was hoping someone on here would be able to provide me an answer.

Many thanks in advance.
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Postby mith » Tue Sep 11, 2007 8:34 pm

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Postby blcr11 » Tue Sep 11, 2007 9:24 pm

In effect, you are putting things in an oven and baking them to 140-150 C when you sterilize solids on the dry cycle of an autoclave. You don't need steam for solids - and you could just as well bake them in an oven for sterilization provided you get the temperature high enough. You need the high pressue to superheat steam, and you need the steam to keep liquids from boiling away when you autoclave culture media. The liquid cycle of an autoclave is essentially a big pressure cooker.
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Postby canalon » Wed Sep 12, 2007 1:40 pm

Just a quick note:
-You can replace an autoclave by a pressure cooker (I used to do that in one lab we worked with for small batches of media)
-You cannot replace it with an oven set at 120ºC. Steam is important for proper sterilization. Proper dry sterilization by heat is done between 350ºC and 400ºC for a few hours.
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Postby Alvino » Wed Sep 12, 2007 3:40 pm

Excellent information & sincere thanks to you guys, however that pretty much leads to my next question.

I always thought that it was the heat that killed of the bacterial spores, but you say steam is required also. Do you know what the steam actually does to aid in the sterilsation process?

I've been told by someone that the high pressure of the steam molecules has a "kind of bullet approach" bouncing around the autoclave that penetrate the cell wall membrane of a virus, bacteria, bacterial spore, fungii or prion. Once it does that it renders that cell denatured.

It sounds plausible, however I just wanted a second opinion.

Again, many thanks for your inputs so far.
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Postby canalon » Wed Sep 12, 2007 6:12 pm

Honestly, I do not really know.
The person who told me that was fully qualified but a pure pain in the *** . So I did not try to inquire further.
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