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GAUTAM Kumar <pk2gkcom@gmail.com>
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🟥Water
Sat, 24 Dec, 2022 at 12:38 pm
CULTURE MEDIA
Basic constituents
1.
2. Electrolyte: Sodium chloride or other electrolytes.
3.Agar
5. Blood or serum; 5-10% defibrinated sheep blood.
4. Meat extract: 'Lab- lemco. It contains protein degradation products, inorganic salts, carbohydrates and growth
factors.
3. Peptone: partially digested proteins.
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• It is prepared from sea weed (Algae- geladium species).
Agar:
• It contains mainly long-chain polysaccharide, a small amount of protein-like material and a variety of inorganic salts.
• It is available either in powder form.
• It is used in concentration of 2%.
• It melts at 98°C and usually solidifies at 42°C.
• Agar does not provide any nutrition to the bacteria but acts as a solidifying (jellifying) agent only.
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TYPES OF MEDIA
1. Based on physical state
» 1. Liquid media
» 2. Semisolid media
» 3. Solid media
2. On the basis of presence of molecular oxygen and reducing substances in the media
» 1. Aerobic media 2. Anaerobic media
3) Based on nutritional factors
1. Simple media
2. Complex media
3. Synthetic media
4. Special media
(a) Enriched media
(b) Enrichment media
(c) Selective media
(d) Differential media
(e) Indicator media
(i) Transport media
(g) Sugar media
(a) Enriched Media » When basal medium is added with some nutrients such as blood, serum or egg, it is called
riched medium.
eg:
2. Chocolate agar - It is a heated blood agar used for isolation of Neisseria and Haemophilus influenza
3. Loeffler's serum slope-Serum is added for enriching the medium. used for Corynebacterium diphtherias.
(b) Enrichment Media : liquid media, contain substances inhibitory & stimulating.
Example:
1. Tetrathionate broth where the tetrathionate inhibits coliforms while allowing typhoid-paratyphoid bacilli
(salmonella) to grow freely,
2. Selenite F broth for dysentery Bacilli PRIYA
3. Alkaline peptone water(APW) for vibrio cholerae
(c) Selective Media » is solid media, contain substances inhibitory & stimulating.
Examples:
• Deoxycholate citrate agar (DCA) → Salmonella and shigella
• Lowenstein Jensen (LJ) medium → M. tuberculosis
• Mac-Conkey's medium → Coliform bacteria.
(d) Indicator Media: » Media contain an indicator which changes colour when a bacterium grows in them.
Examples: get black colonies
• Wilson and blair medium (reaction sulphite to sulphide) → S.typhi
• Mcleod's medium (potassium tellurite)( reaction metallic to tellurium) → C. diphtheriae
(e) Differential media: in which different bacteria produced different colours.
Ex-
1) Mac conkey's media: » which contains peptone, lactose, agar, sodium.
1. The lactose-fermenter (LF)- pink coloured colonies
2. Non-lactose fermenters (NLF) - produce colourless or pale colonies.
2) Xylose Lysine Deoxycholate (XLD)Agar: » Used for the recovery of Salmonella and Shigella species.
3) Thiosulfate-citrate-bile salts-sucrose agar(TCBS) : » highly selective for the isolation of V. cholerae and Y.
parahaemolyticus.
(f) Transport Media : » For transport of specimens to the laboratory.
→ Transport media for stool specimens
• Cary-Blair → All enteric organisms
• Stuart → All enteric organisms
• Amies → All enteric organisms
• Buffered glycerol saline → All enteric organisms except Vibrios ,Campylobacter
• Alkaline peptone water → Vibrios
• V-R fluid → Vibrios