Culture media

microbiology

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

4. CONTD…..

5. CONTD…. 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.

6. Contd … - 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).

8. Contd … Meat extract, Yeast extract: These contain protein degradation produc t , 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: On the basis of physical state, media are used in the three forms; - Solid - semi- solid - Fluid

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12. Contd … 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.

13. Contd … 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.

14. Contd … 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.

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

16. Contd … 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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