Endotoxins and moist heat sterilization

Hi guys and Happy new year,

I know that gram negative bacteria, if destroyed, release endotoxins. So they originate from gram negative bacteria after death.

Moist heat sterilization in autoclave aims to kill the bacteria.

So why do we only use biological indicator of geobacyllus stearotermophilus during autoclave qualification and not endotoxins?

Thank you

Moist heat sterilization (Autoclave) aims to kill the bacteria and NOT the endotoxins. Hence, for the qualification of an autoclave, endotoxins are not used.
Autoclaves use saturated steam under pressure of approximately 15 pounds per square inch to achieve a chamber temperature of at least 250°F (121°C), usually 30–60 minutes, for a prescribed time. At these conditions, the pyrogens (endotoxins) can not be destroyed.

Please note that depyrogenation is a process that removes pyrogens (Endotoxins). The most prevalent and problematic pyrogens are the bacterial endotoxins found in the outer cell walls of gram-negative bacteria. Thus, depyrogenation is a process that will either destroy or remove bacterial endotoxins.
In a depyrogenation process, a commonly used minimum time and temperature is 30 min at 250 °C.


Thanks for your kind reply.
Ok, endotoxins are not used for qualification of an autoclave.

This means that when we want to verify the sterilization of a filling machine components in autoclave, e.g. filling needles, we do not have to care about endotoxins? Isn’t there a chance of endotoxins in that case?

Hi Pasquale, that is a very valid and interesting question; I hope I can address it clearly here.

Short version: the need to depyrogenate filling needles depend on the risk of endotoxin contamination of the product being filled.

Historically, filling needles are depyrogenated by rinsing using WFI, given the technological limitations of other depyrogenation processes like dry heat, filtration or acid-base solutions; however, this method is not very relyable and hard to validate.

Current industry and regulatory expectation is that this risk of endotoxin contamination needs to be addressed in a Contamination Control Strategy (CCS), as indicated in PIC/S annex 1, or similar document embedded in the QMS of your site. Meaning that if the risk of pyrogen contamination of the product being filled is high even with the controls that are in place (e.g. CIP/SIP), then the need to adopt and validate a depyrgenation process is expected.

Because of this, equipment manufacturers are opting to implement NO2 (gas) depyrogenation to their technologies, and it is expected to become an industry standard for asspetic technologies, like Blow Fill Seal (BFS) processes.

I hope this can give a little more clarity on the matter. Let me know if you need me to elaborate further.

Hi Andres,
you could not be clearer than that.
Therefore, a pyrogen risk-based approach. I will find out more about PIC/S annex 1 and also NO2 depyrogenation.
Thanks for your suggestions!

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