Stock culture mahadi ppt

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Microorganisms are kept for:
Control the culture media (testing
media).
Control the biochemical &
sensitivity testing.
For teaching purpose.
For further identification.

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The bacteria are vary in their ability
to remain a life after they complete
their growth. There are different
methods for preservation of
microorganisms:
Moist storage.
Cold storage.
Dry storage.
Freeze drying storage (The best one).
In this method keep the organisms
by serial subculture (interval time)
to keep it is life.
Use different types of media
according to the type of
microorganisms
Choice media with low nutritional
substances.
Semi-solid media (Nutrient agar).

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Cooked meat media (CMM).
Blood broth.
Dorset egg.
Egg saline.
Skimmed milk.
Semi-solid media:
Staphylococci: Subculture every 1-2 month.
Enterobacterieace: Subculture every 3
month.

Blood broth:
Streptococci: all of them except
pneumococci every one month.
Dorset egg, Egg saline & skimmed
milk:
Used for many organisms at least every 6
month subculture.
CMM:
Clostriia: subculture every 6-12month.

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Method:
Use screw capped container.
After inoculation (stabbing), incubate
over night.
Sealing by paraffin wax – fill the
container.
Make at least duplicate every organism.
Advantage:
Easy.
Practical.
Disadvantage:
Cannot prevent mutation.
There is chance for drying &
contamination.

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Use low temperature for
preservation the microorganisms.
Use different degree of temperature:
4 - 8 C° domestic refrigerator.
-20 C° - -40 C° deep freezer.
-70 C° - -80 C° ultra deep freezer.
-70 C° solid CO
2 (Micro-bank methods).
-196 C° liquid nitrogen methods.
Some organisms like Niesseria and H.
influenzae cannot preserve by this method.
4 - 8 C° or -20 C° - -40 C° keep the organisms
for short time.
-70 C° culture the organism in tube and then
inserted in container CO
2.
Adv. : keep organism for long time – no change
and no need for subculture.

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Disadv. : expensive – regular filling with
CO
2.
-80 C° ultra deep freezer:
When used it need certain precautions to
avoid ice crystals and concentration of
salt (destroy the organisms) by using:
Glycerol – Sugar – Dimethyl sulphoxide
(DMSO).
-196 C° (liquid nitrogen):
Rapid freezing and rapid rewarming will
avoid formation of ice crystal, and viability
does not affected.

Disadv: have some disadvantage of
CO
2.
Micro-bank system:
Commercial supplied cryovials which
are screw capped 2ml container.
Method: Bacterial suspension add to
the vial which contain
cryopreservative. The organism
absorbed by the glass beads in the vial,
the excess fluid is absorbed and
discarde (storge at -70 C°).

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Done by several method:
Filter paper disc methods: Thick
suspension of organism is prepared,
and impregnate the disc of filter paper
with it. Drying take place in a desiccant
under vacuum, over reducing
substance such as phosphorus peroxide
(P
2O
5), and lastly impregnated with
paraffin oil.
Slamp method: Similar to previous
method
with some modification in the
reducing substance which is
incorporated in the medium (10%
gelatin with ascorbic acid – paper is
impregnated with the paraffin oil
before the culture – dry as describe
above).
L. method (La page method):
Drying in bottle or prefer tubes or
capillary tube seal it and kept for long
time.

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