Microbe Heat Resistance and Autoclave Testing

[jamesrc]

Hi,
Does anyone know of a good reference for heat resistance of microbes? What would really help would be any listing of decimal reduction times (D-values) at a given process temperature and z values. I'm just trying to make sure our autoclave kills everything it's supposed to for someone, so I've got a list of microbes with initial # of colony forming units from some bioburden studies. If anyone can point me towards a good reference, that would be a big help. Thanks.

 

[cronxeh]

Autoclave doesn't kill certain archaebacteria

Edit: Ok I dug up some info for you:

Pyrolobus fumarii holds the current record for heat stability, with a 106 deg C temperature optimum and 113 deg C maximum - it is so heat tolerant that it is not killed by one-hour treatment in an autoclave (121 deg C)!

Also there are pH-tolerant archaebacteria that grow in highly acidic (pH=0.7) and highly basic (ph=11) environments.

And then there are pressure-tolerant archaebacteria that have been isolated from ocean depths and requiring pressures of 300 atm just to survive, and tolerating up to 800 atm.

 

[DocToxyn]

In terms of practical use of autoclaving for the destruction of your typical contaminating species I would guess that the standard protocols remove 99%+ of the bacteria on your surfaces. Unless you, or your colleagues, are directly working with them, the chances of you running into any of the extreme-environment tolerant species is minimal.
If you are looking for some sort of laboratory-based testing or verification to reach some clinical threshold you might try a company like http://www.namsa.com/index.asp" for you to test the efficacy of your autoclave. You can either try some of their products or maybe call their tech support for some free advice.

 

[quark]

Fedegari has an excellent write up on F0 calculation. You can access the document at http://www.fedegari.com/techno.asp#fo

I read somewhere that Stain121, which generally stays in the ocean depths, can resist the moist sterilization temperatures of 121 deg.C

 

[jamesrc]

Thanks for all of the help everyone. We had tried using spore strips for the validation, but the FDA wasn't satisfied. I found a few books that were helpful, especially Thermobacteriology in Food Processing by Stumbo. I think I've managed to find enough references to show that all of the microbes on my list are easier to kill than B. stearothermophilus, so I'm OK. Then again, I don't know jack squat about microbes and had never even heard of an autoclave a month ago. Thanks again.

 

[No-where-man]

Fedegari has an excellent write up on F0 calculation. You can access the document at http://www.fedegari.com/techno.asp#fo
I read somewhere that Stain121, which generally stays in the ocean depths, can resist the moist sterilization temperatures of 121 deg.C

And tardigrades can survive +150 degrees without water,they are pretty much indestructible as bacterias.

 

[Moonbear]

Usually the testing kits for autoclaves are intended to detemine if your autoclave is actually working properly, not whether it is supposed to kill certain bacteria at a particular setting.

If you're working with a specific bacteria that you're concerned about surviving extreme environments, I would think the safest approach would be to autoclave media known to contain the bacteria, and then culture it after autoclaving to see if they survived.