keeping reference-strains

ChrisEmAmb chrisemamb at aol.com
Fri Aug 11 15:57:58 EST 2000

Hi Hec,

I assume you are talking about Salmonella.  The best way to store your cultures
long-term is by putting them onto Dorset's eggs slopes; these are Bijoux
containing a suspension of whole hen's egg in saline, which has been "cooked"
on a slope within the bijoux container.  A loopful of a fresh culture of your
strain, inoculated onto a Dorset's egg slope, will last around 5 years
(although I have several in my lab which are over 10 years old!).  You should
also take a suspension of your bacteria to freeze down at -80 degrees C.  To do
this you can make a brain-heart infusion broth containing10% glycerol,
sterilise, mix with your culture, and then store this mixture on glass beads in
pre-prepared vials.  The beads mean that you can take an aliquot of your
bacterial culture without having to freeze-thaw your culture too much.  If all
of this sounds like hard work, the pre-prepared beads in solution are available
commercially from any good microbiology supplier - Prolabo is our supplier. 
Dorset's egg slopes are also available commercially from Oxoid.  

I would suggest you store your cultures using both methods - Dorset's egg
slopes are great because they are kept at room temperature and so require no
specialist equipment.  They are also easy to dip into when required (using good
aseptic technique, of course :-) )  Frozen cultures will keep for much longer.

I hope this helps.

Dr. Emma Allen-Vercoe

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