Yersinia yersinia at CYBERNEX.NET
Tue Mar 30 13:40:57 EST 1999

Angelika Florvaag writes,

<When Plate Count Agar is used to enumerate Bacillus spp., the samples are
heated at 80ƒC for 20 min. prior to plating. Both vegetative cells and
spores survive this treatment so I suppose it's possible to find vegetative
forms of Bacillus after the heat treatment you mentioned.>

Vegetative cells survive the 20-minute heat-shock at 80C?!  Really?! At a former job (in a pharmaceutical company), one of my responsibilities was stock culture prep and maintenance. For B. cereus, I had to make spore suspensions instead of freeze cultures (as I did with the other organisms except for the mold A. niger which was also a spore suspension). Though it's been a couple of years since I worked there and did this, I distinctly recall following the SOP which specifically stated performing a 20 minute heat shock at 80C!! 

So in the event I ever do stock culture maintenance again and need to make spore suspensions of B. cereus, what temperature *does* kill the vegetative cells and for how long should the heat shock last?


I am, therefore I'll think.

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