The document discusses culture media used to grow microorganisms in clinical laboratories. Culture media contains basic nutrients necessary for microbial growth and development. Agar is commonly used to make solid culture media and is obtained from seaweed. It melts at 98°C and solidifies at 42°C. Culture media can be classified based on physical state (solid, semi-solid, fluid), chemical composition (natural, semi-synthetic, synthetic), or purpose (basal, enriched, selective, differential). Basal media are simple and routinely used while enriched media add substances like blood or serum to support more nutritionally demanding bacteria.

1. CULTURE MEDIA
MAN BAHADUR RANA
BPH
ACAS,NEPAL

2. INTRODUCTION
The culture media is used for growth
and identification of microorganisms in the
clinical laboratory. Microorganism, like all
other living organism, requires basic
nutrients, for their growth and development
The food material on or in
which microorganisms are grown in the
laboratory is called a culture medium and the
growth itself is called a culture.

3. HISTORY

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Agar:
- Used for preparing solid medium.
- Obtained from seaweeds.
- Its chief constituent is a long chain
polysaccharide, mainly composed of D-
galactopyranose units.
- No nutritive value.
- Not affected by the growth of bacteria.

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- Melts at 980C and sets at 420C
- Approximately 2% agar is used for solid
media.
- The jellifying property varies in different
brands of agar: e.g New Zealand agar has
more jellifying capacity than Japanese agar.

7. Composition of Media
The basic constituents of basal culture
media are as follows:
 Water: Sources of hydrogen and Oxygen.
 Electrolyte: Sodium chloride or other
electrolytes.
 Peptone: Partially digested proteins prepared
from animal or vegetable protein(heart
muscle, casein or soya flour) by enzymatic
action(such as pepsin, trypsin or papain).

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 Meat extract, Yeast extract: These contain
protein degradation product, carbohydrate,
inorganic salt and certain growth factor. Meat
extract is commercially available as lab-lemco.
 Blood: It enriches media. Usually, 5-10%
defibrinated horse or sheep blood is used.
 Agar or (agar-agar): It is derived from sea
weed. (Algae: Geladium species.)

9. Types of culture media
Culture media have been classified in
many ways:
1. On the basis of physical state, media are used
in the three forms;
- Solid
- semi- solid
- Fluid

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On the basis of chemical composition, there
are three main types of culture media.
- Natural or empirical culture media.
- Semi-synthetic culture media.
- Synthetic culture media.

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Natural or empirical culture media:
Those media whose exact chemical
composition is not known are called natural or
empirical culture media. e.g milk, urine,
vegetable juices.
Semi-synthetic culture media:
Those media whose chemical
composition is partially known are called semi-
synthetic media. E.g potato dextrose agar.

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Synthetic culture media:
Those media whose chemical
composition is exactly known are called
synthetic media.
e.g peptone water: 1%peptone
+0.5% Nacl in water.

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On the basis of Utility purpose:
- Basal Media (Basic media)
- Complex Media.
. Enriched media
. Enrichment media
. Selective media
. Differential media
. Indicator media
. Transport media

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Basal Media (Simple media):
This is the simplest media and
routinely used in the laboratory for diagnostic
purpose. It consist of peptone, meat extract,
sodium chloride and water.
e.g Nutrient Agar
Nutrient broth
NB + 2% Agar= Nutrient agar.

17. Complex Media
Enriched Media:
- Substances like blood , serum, egg are
added to the basal medium.
- Use to grow bacteria that are exacting in
their nutritional needs.
e.g Blood Agar
Chocolate Agar

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