Re: Tryptone broth test for sterility check

msalguod@xxxxxxxxx wrote in news:1143208044.677180.69360
@t31g2000cwb.googlegroups.com:

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.


Subculture to check if it?s growth or a deposit. Plating onto a blood agar
is usually sufficient or you could put about 0.1ml of the contaminated
sample into a another broth.
There?s always a chance of contamination when adding the broth.
I have seen deposits due to the powder used to clean the glassware.

Dave
.

Relevant Pages

  • Re: Tryptone broth growth for sterility check
    ... (after autoclaving) ... was growth or some sort of precipitation. ... ISTR using an upside down mini test tube in the big test tube of ...
    (sci.chem)
  • 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)
Loading