Transcript Culture Media

Culture Media
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Culture Media:
is a medium (liquid or solid) that contains nutrients to
grow bacteria in vitro. Because sometimes we cannot
identify with microscopically examination directly, and
we do culture for antibiotic sensitivity testing
Note: media are sterilized by autoclaving at 121°C. With
the autoclave, all bacteria, fungi, viruses, and spores
are destroyed. Some media can’t be sterilized by
autoclaving because contain eggs or carbohydrates.
Properties of Media
Support the growth of the bacteria.
Should be nutritive (contains the required amount of
nutrients).
Suitable pH ,temperature and suitable atmosphere).
(Bacteria grow at 370C).
There are three physical forms of media
1- Liquid, or broth media
 2- Semisolid media
 3-Solid media.
 The major difference among these media is
that solid and semisolid media contain a
solidifying agent (usually agar),
whereas a liquid medium does not.
 Liquid media, such as nutrient broth,
tryptic soy broth, or brain-heart infusion
broth can be used to grow large numbers of
microorganisms in fermentation studies and
for various biochemical tests.
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Liquid media is best when you want to 
rapidly increase the concentration of the
organism or when you want to grow motile
cells. The growth in liquid media:
1.Surface growth pellicle, 2.uniformly
turbid,
3. Sediment in bottom 
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Semisolid media can also be used in
fermentation studies, in determining
bacterial motility and in promoting
anaerobic growth.
Solid media
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such as nutrient agar or blood agar, are
used
(1) for the surface growth of
microorganisms in order to observe colony
appearance,
(2) For pure culture isolations,
(3) For storage of cultures,
(4) To observe specific biochemical
reactions
Culture media for bacterial
growth
 Some
bacterial species are
able to grow under wide range
of conditions , but others are
very fastidious.
Types of Culture Media 
Simple culture media: are media that 
contain the basic nutrients (growth
factors) that support the growth of bacteria
without special nutrients, and they are
used as basis of enriched media. E.g.
Nutrient broth, nutrient agar, peptone water.
They are for the growth of non-fastidious
organisms like E.coli.
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Enrichment media:
Such as (blood agar, serum agar) are
prepare to meet the nutritional equipment of
more exacting bacteria by the addition of
substance such as blood , serum , egg, to
basal medium
Selective media :: it is a mediam, which
contains inhibitor substances that prevent
the growth of microorganisms other than the
bacteria for which the media is prepared for.
For example: Mannitol salt Agar (MSA)
Differential Media
it is a mediam, which contains a carbohydrate source 
and indicator to differentiate microorganisms based on
their ability to ferment carbohydrate to produce acid
end-products which react with the pH indicator and
change its colore.g. MacConkey agar, which contains
neutral red (pH indicator) and is used to differentiate
lactose fermenter (E. coli )and non-lactose fermenter
(Salmonella).the Organisms ferment lactose and produce
acid end-products which react with the pH indicator
neutral red, and produce a pink color. If the bacteria are
non- lactose fermenter it will utilize protein source and
produce alkaline products which react with pH indicator
neutral red, and produce a pale yellow color.
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nutrient agar,
- Chocolate Agar
Blood Agar
Mannitol salt Agar (MSA)
- MacConkey Agar
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media
classification
Selective agents
Type of
organisms
isolated
nutrient agar,
simple
basic nutrients
E.coli.
Chocolate agar
enriched
1%hemoglobin
Most fastidious
pathogens such
as neisseria and
Haemophilus
Blood agar
Enriched and
differntial
5%defibrinated
sheep blood
Almost all
bacteria
differntial for
hemolytic
organisms
Maconkey agar
Selective and
differntial
Lactose ,bile
salt ,crystal
violet
Gram negative
enteric bacilli