I wonder if somebody could assist us with the following questions.
We use 70% isopropyl alcohol to disinfect our clean hoods. We, as a safety measure, usually filter the alcohol thorough a 0.22 micron filter to remove possible spores.

1. Is this a necessary thing to do? Would spores survive in alcohol at all?
2. If we were to transfer the filtrate on a growth plate, how much time

Later should we check for growth? Is a 3-day period in the incubator sufficient?

Thank you for any help.
Sincerely,
Eszter Soos
Pharmacist
Toronto, ON
Canada

Dear Mrs Soos,

1. In general, one can state that spores can persist in alcohol and are not destroyed or inactivated like bacteria, fungi or certain viruses. A spore filtration is hence an indispensable step to make sure that the alcohol you use is spore-free. Usually, a filter with a pore diameter of 0,45 micrometer is used for spore-filtration. Your 0,22 micron filter is consequently more than sufficient to ensure that the alcohol you use is spore-free.
2. Spores can very well be incubated on growth media. Under optimal conditions and in an appropiate growth broth, it usually takes about 24 hours to see first results. Your three day incubating period should therefor be enough time to determine any growth.

Kind regards,
Annette Rittich
Marketing
Bode Chemie Gmbh & Co