Re: Tryptone broth growth for sterility check

DSRM wrote:
We've started testing our microbiology dilution water for sterility
(after autoclaving) by adding some double strength tryptone broth and
incubating for 24 hours. I've never done this before.

What exactly constitutes growth?

Our first test had alot of what looked like white sediment on the
bottom of the sample and the smple was cloudy. I wasn't sure if this
was growth or some sort of precipitation.
I set another batch and I purposely contaminated some and put in some
plain DI water. Still they all looked the same.

I checked the autoclave settings and saw that they had it set for the
mininum 15 minute hold at 122° C.

I tried another batch with a 30 minute hold. The contaminated samples
still looked the same but the uncontaminated samples were only a
little cloudy. It made no difference whether the bottles were in the
middle of a cluster with no air space between them or if they were
alone with plenty of surface exposure.

Does the cloudiness constitute growth (I think it does)?

Do you find that sterilization of water requires more than a 30 minute
hold time?

Thanks.

Very rusty....(UK "A" level, way, way back in '75.) Are you looking for
coliforms? ISTR using an upside down mini test tube in the big test tube of
broth (the small tube is full of liquid), then when the gas producing
bateria multply the gas collects in the tiny tube and the observation of a
large bubble of gas gives you a positive result.


--
Ron Jones
Process Safety & Development, Alfa Aesar Avocado Lancaster UK
Don't repeat history, see unreported near misses in chemical lab/plant
at http://www.crhf.org.uk
Only two things are certain: The universe and human stupidity; and I'm
not certain about the universe. ~ Albert Einstein


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Relevant Pages

  • Re: Tryptone broth test for sterility check
    ... (after autoclaving) ... was growth or some sort of precipitation. ... I tried another batch with a 30 minute hold. ... Do you find that sterilization of water requires more than a 30 minute ...
    (sci.bio.microbiology)
  • Re: Tryptone broth test for sterility check
    ... (after autoclaving) ... was growth or some sort of precipitation. ... sample into a another broth. ... There?s always a chance of contamination when adding the broth. ...
    (sci.bio.microbiology)