Culture Media Flashcards by Richhpal Singh

Origin of Agar

Seaweeds (red algae of galidium and gracilaria)

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Composition of agar

Polysaccharide - Agarose and Agaropectin

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Nutritional value of Agar

None

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Melting and Solidifying temperature of Agar

Melts >98°C
Solidify <42°C

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Concentration of Solid, semisolid and Firm agar

Solid - 2% agar
Semisoild - 0 5% agar (Motility testing)
Firm - 5-6% agar (inhibit swarming motility - Proteus)

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Simple media/ Basal medium / Basic medium

Only Non fastidious organisms will grow
Peptone water

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Composition of Peptone water

Peptone - 1%
Nacl - 0.5%
Water

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Nutrient broth Composition

Peptone water + 1% meat extract

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Nutrient agar composition

Nutrient broth + 2% Agar

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Enriched medium used to grow

Used to grow fastidious organisms
Egg/blood/serum is added to provide extra nutrition

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Enriched medium includes

Blood agar
Chocolate agar
Loeffler’s serum slope
Lowenstein Jensen medium

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Blood agar

Autoclaved nutrient agar cooled to 50°C
5-10% sterile sheep RBC
Enriched + differential media

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Chocolate agar

Autoclaved nutrient agar cooled to 70°C
5-10% sterile sheep RBCs
More nutritious - Release factors V and X

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Loeffler’s serum slope used to grow

Corynebacterium diphtheria (Klebs Loeffler bacilli)
6-8 hours to grow

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Composition of Lowenstein Jensen media

Tuberculosis
Coagulated hen’s egg
Mineral salt solution
Asparagine
Malachite green

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All culture media are sterilized by

Autoclave except Loeffler’s serum slope and Lowenstein Jensen media

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Enrichment broth

Liquid media that is selective in nature

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Examples of Enrichment Broth

Alkaline peptone water
Selenite F broth
Tetrathionate broth

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Which organism used to grow on Alkaline Peptone water

Vibrio

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Organisms grown on Selenite F broth and Tetrathionate broth

Salmonella and Shigella

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Selective media

Addition of components to inhibit selected bacteria

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Composition of MacConkey agar

PLANT
Peptone
Lactose - Differential media
2% Agar
Neutral red - Indicator media
Taurocholate - Selective media

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Composition of Mannitol salt agar

Selective media - Salt (allows S. Aureus to grow)
Differential media - Mannitol fermenter +/- : Yellow
Indicator media - Phenol red

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CLED Composition

Cysteine lactose Electrolyte deficient
Differential media - LF +/-
Selective media - Lactose
Indicator - Bromothymol blue

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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)

CVBA used a selective media for which organism

S. Pyogenes

Modified Thayer Martin is used as selective media for which organism

N. Meningitidis N. Gonorrhea

Cetrimide agar is used as selective media for which organism

Pseudomonas

DCA And XLD used as selective media for which organism

Deoxycholate citrate agar Xylose lysine deoxycholate Used for Salmonella and Shigella

Potassium tellurite agar is used as selective media for which organism

Corynebacterium diphtheria - Black color

PLET is used as Selective media for which organism

Polymxin lysozyme EDTA thallous acetate Used for B. Anthracis

MYPA and PEMBA used as Selective media for which organism

Bacillus cereus

Differential media used for lactose fermenters

MacConkey CLED

Differential media used to differentiate Alpha, beta and gamma Hemolysis

Blood agar

Differential media used to differentiate Sucrose fermenter

TCBS (Thiosulfate citrate bile salt sucrose)

Differential media used to differentiate Mannitol fermenters

Mannitol Salt agar (MSA)

Transport media are used to maintain

Vitality of bacteria

Amies And Stuart media used as Transport media for which organism

Neisseria

Pike's Media used as Transport media for which organism

S pyogenes

Carry Blair medium is used as Transport media for which organism

Vibrio cholera

SBGS used as Transport media for which organism

Sachs buffered Glycerol saline For Salmonella and Shigella

Media to grow Anaerobic bacteria

Robertson Cooked meat broth

In case of Proteolytic reaction on RCMB, meat color turns into

Black - C tetani

In case of Saccharolytic reaction on RMSB, meat color turns into

Pink - C. Perfringes

Where to keep slide to maintain Anaerobiasis

Keep slide in Mc Intosh and Fildes anaerobic jar

Method of choice for Anaerobiasis

GASPAK

Culture Techniques

Streak culture Stroke culture Lawn culture Gelatin stab culture

Culture Technique to obtain pure colonies

Streak culture

Uses of Stroke culture

Provide a pure growth for bacteria of slide agglutination and other Diagnostic methods

Lawn culture is also known as and its uses

AKA - Carpet culture Used for - Antibiotic sensitivity testing, Preparation of Bacterial antigens and vaccines Bacteriophage typing

Gelatin stab culture Examples

Inverted fir tree appearance - B. Anthracis Fir tree appearance - C. Tetani Napiform/turnip appearance - V. Cholera

Difference between Pour plate and spread plate method

Pour plate - Add bacteria then add agar on top of it Bacterial growth going to be noted under the surface also Spread culture - First agar then add bacteria

Minimal inhibitory concentration definition

Lowest concentration of bacteria that inhibits the growth of pathogen in medium

Minimal bactericidal concentration (MBC) Definition

Minimum concentration of antibiotics that kills the bacteria in a medium

At what MIC, Bacterial growth is inhibited

4microgm/ml

Methods of antibiotics sensitivity testing

Dilution method Disc Diffusion method Stokes disc Diffusion method Epsilometer test Automated methods

Dilution method procedure

Inoculum prepared - add E coli to sterile peptone water and incubate - After growth measure the turbidity using Sphectrophotometer/McFarland's standard media

0.5 MacFarlands is equal to

1.5 x 10^8 CFU/ml

Types of Dilution broth

Mircobroth - 96 wells plate, Saves medium and time used Macrobroth - Done in test tubes, requires time

Disc Diffusion method is also known as

Kirby Bauer Disc Diffusion method

Agar used for disc Diffusion method/Kirby Bauer Disc Diffusion method

CAMHA (Cation adjusted mueller Hinton agar)

Disc Diffusion method procedure

Lawn culture - Incubate overnight - Disperse Antibiotic disc (25mm distance) - overnight incubate at 37°C

Interpretation of Disc Diffusion method and Disadvantage

Observe zone of inhibition around each disc If zone of inhibition present - Sensitivity +ve If absent - Resistant Measure diameter of Zone inhibition Disadvantage - No quantification (MIC)

Strokes disc Diffusion method

All others same as Disc Diffusion method Added control Strain and comparison provided

Epsilometer test

Provides MIC Strip is used to differentiate concentration of antibiotics

Example of Automated method

VITEK

Culture Media Flashcards

(68 cards)