how to kill B. subtilis spores?

Dr. Michael J. Miller mignatz at mjmiller.roc.servtech.com
Mon Dec 4 20:21:54 EST 1995

The best bet is to autoclave your spatula at 121 deg. C for 15 min.

Chemical agents that have sporicidal claims include higher concentrations
of hydrogen peroxide (30%), peracetic acid (30%), and glutaraldehyde
(J&J's Cidex).  You will require a longer soak time to kill these spores
than if you use an autoclave, unless you want to use ethylene oxide

If you choose to test a chemical agent, inoculate a surface with about one
million spores (eg in 10 microliters).  Flood the area with the chemical
agent and let sit (eg, 15 min).  Then sample the inoculated area with a
swab (and transfer to a TSA plate), or better yet, with a RODAC plate (TSA
with neutralizers).  After incubation at 30-35 deg C, if there's growth,
the agent didn't kill all the spores at the soak time tested.

Once again, autoclaving is the best...wrap a whole bunch of spatulas and
sterilize them all at the same time.  Make sure that your autoclave will
reach 121 or you may not kill the spores (you can check this with
biological indicators using B. sub. var. niger or stearothermophilus. 
Good luck!


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