Culture Media Flashcards
Origin of Agar
Seaweeds (red algae of galidium and gracilaria)
Composition of agar
Polysaccharide - Agarose and Agaropectin
Nutritional value of Agar
None
Melting and Solidifying temperature of Agar
Melts >98°C
Solidify <42°C
Concentration of Solid, semisolid and Firm agar
Solid - 2% agar
Semisoild - 0 5% agar (Motility testing)
Firm - 5-6% agar (inhibit swarming motility - Proteus)
Simple media/ Basal medium / Basic medium
Only Non fastidious organisms will grow
Peptone water
Composition of Peptone water
Peptone - 1%
Nacl - 0.5%
Water
Nutrient broth Composition
Peptone water + 1% meat extract
Nutrient agar composition
Nutrient broth + 2% Agar
Enriched medium used to grow
Used to grow fastidious organisms
Egg/blood/serum is added to provide extra nutrition
Enriched medium includes
Blood agar
Chocolate agar
Loeffler’s serum slope
Lowenstein Jensen medium
Blood agar
Autoclaved nutrient agar cooled to 50°C
5-10% sterile sheep RBC
Enriched + differential media
Chocolate agar
Autoclaved nutrient agar cooled to 70°C
5-10% sterile sheep RBCs
More nutritious - Release factors V and X
Loeffler’s serum slope used to grow
Corynebacterium diphtheria (Klebs Loeffler bacilli)
6-8 hours to grow
Composition of Lowenstein Jensen media
Tuberculosis
Coagulated hen’s egg
Mineral salt solution
Asparagine
Malachite green
All culture media are sterilized by
Autoclave except Loeffler’s serum slope and Lowenstein Jensen media
Enrichment broth
Liquid media that is selective in nature
Examples of Enrichment Broth
Alkaline peptone water
Selenite F broth
Tetrathionate broth
Which organism used to grow on Alkaline Peptone water
Vibrio
Organisms grown on Selenite F broth and Tetrathionate broth
Salmonella and Shigella
Selective media
Addition of components to inhibit selected bacteria
Composition of MacConkey agar
PLANT
Peptone
Lactose - Differential media
2% Agar
Neutral red - Indicator media
Taurocholate - Selective media
Composition of Mannitol salt agar
Selective media - Salt (allows S. Aureus to grow)
Differential media - Mannitol fermenter +/- : Yellow
Indicator media - Phenol red
CLED Composition
Cysteine lactose Electrolyte deficient
Differential media - LF +/-
Selective media - Lactose
Indicator - Bromothymol blue
Which one is better CLED or McConkey agar
CLED > MacConkey
Because CLED allows both gram+ve and -ve to grow
TCBS Composition
Thiosulfate citrate Bile salt sucrose
Selective medium - Bile salt
Differential media - Sucrose fermenter +/-
Indicator - Bromothymol blue
On TCBS , color shown by sucrose fermenters and Non Sucrose fermenters
Sucrose fermenter - Yellow color (V. Cholera)
Non Sucrose fermenter - Green color (V. Parahemolyticus)