Spiked stoppers + metal

hi all

This is a new thread but is linked to an old question i had up on this forum regarding the validation of stopper processing cycles.

I would like to hear theories from anyone with any experience in using stoppers spiked with geobacillus stearothermophilus.

i recently ran some trial cycles using spiked stoppers. the cycles ran were typical for validation settings, i.e 20 minutes at 121C with washing. the main difference between cycles which showed positive growth after incubation and those that didn’t was the set up of the stoppers. initially i used untreated paperclips. they were flamed then stoppers were threaded on. Subsequently i depyrogenated the paperclips prior to use. the cycles ran with stoppers threaded on to depyrogenated paperclips were successful.

Does anyone have any theories on why or how this would make a difference?