Types Of Culture Media
1) Basic medium:
Typically composed of peptones, extracts, salts, and water.
It is a medium containing the basic nutrients for the growth and reproduction of general microorganisms.
Examples:
Nutrient Agar:
Tryptic Soy Broth (TSB).
pH is adjusted to neutral (7.4) at 25 °C.
It is frequently used for isolation and purification of cultures.
Composition: 0.5% Peptone,0.3% beef extract/yeast extract,0.5% agar,0.5% NaCl, Distilled water.
It is used for confirmation of Campylobacter jejuni by motility test. It is suitable for the cultivation of both aerobic and anaerobic bacteria.
Composition: Peptone, Soybean Digest, Sodium Chloride, Dextrose (Glucose),Water.
2.Enrichment medium:
It may contain blood, serum, vitamins, or other growth factors.
Examples:
It is used to cultivate some microorganisms with strict requirements.
Blood Agar:
Chocolate Agar:
Blood acts as an enrichment material and also as an indicator.
It is particularly useful for the isolation of Streptococcus species, Staphylococcus aureus, and other hemolytic bacteria
Composition: Nutrient agar supplemented with blood (usually sheep or horse blood).
Composition: Prepared by heating blood agar.
It is used for culture of pneumococcus, gonococcus, meningo- coccus and Haemophilus.
Heating the blood inactivates inhibitor of growths.
3.Selective medium.
Examples:
Composition: Selective agents such as antibiotics, dyes, or chemicals are added to inhibit the growth of unwanted organisms.
Its ability to inhibit the growth of certain types of microorganisms.
:
Mannitol Salt Agar
MacConkey Agar
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It is used for isolating pathogenic staphylococci from clinical samples, food and other materials of sanitary importance.
Composition: It is consist of peptones, mannitol, sodium chloride, phenol red indicator, agar, and water.
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This allows only gram-negative species to form colonies on MAC agar.
Composition: This medium include crystal violet dye, bile salts, lactose, and neutral red (pH indicator).
4.Identification medium.
It is to add some reagents or chemicals into the culture medium, so that some changes will occur after culture,
To distinguish different types of microorganisms.
Composition: Besides basal components, indicator media contain pH indicators or other chemical indicators.
Example
Phenol Red Broth
Eosin Methylene Blue (EMB) Agar
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EMB agar is useful in isolation and differentiation of the various gram-negative bacilli and enteric bacilli.
Composition: peptone, lactose, dipotassium phosphate, eosin Y (dye), methylene blue (dye), and agar. There are also EMB agars that do not contain lactose.
Role: prepared with phenol red as an indicator of acid production. A color change from red- orange to yellow occurs when acid is produced as a result of carbohydrate metabolism.
Composition: It consist of dextrose Proteose peptone and beef extract provide nitrogenous nutrients to the organisms.