Questions and Answers
Which of the following are classifications of bacterial culture media based on consistency?
What is a solid medium in microbiology?
Contains agar at a concentration of 1.5-2.0%
How are semisolid media prepared?
With agar at concentrations of 0.5% or less
What does liquid (broth) medium contain?
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Which of these are classifications of culture media based on composition?
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What is a synthetic or chemically defined medium?
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What characterizes a non-synthetic or chemically undefined medium?
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Which of the following are classifications of bacterial culture media based on purpose?
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What is general purpose media?
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What are enriched media?
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What are selective and enrichment media designed to do?
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What is differential/indicator medium?
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What is an example of a selective medium?
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What is the purpose of transport media?
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Which transport medium is used for fecal samples from suspected cholera patients?
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What is Sach's buffered glycerol saline used for?
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What is Pike's medium used for?
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Study Notes
Classification of Bacterial Culture Media
- Culture media can be classified based on consistency into three types: solid, semisolid, and liquid (broth) mediums.
- Solid media typically contain agar at concentrations of 1.5-2.0%.
- Semisolid media have agar concentrations of 0.5% or less, used for motility testing.
- Liquid (broth) media provide specific nutrients without gelling agents like gelatin or agar.
Classification by Composition
- Media is categorized as synthetic (chemically defined) or non-synthetic (chemically undefined).
- Synthetic media have a known exact composition, prepared from purified ingredients.
- Non-synthetic media include at least one impure or variable component, often inconsistent across batches.
Classification by Purpose/Function
- General purpose media support the growth of most non-fastidious bacteria. Examples: Peptone water, nutrient broth, and nutrient agar.
- Enriched media have added growth factors (e.g., blood, serum) for nutritionally demanding bacteria. Examples: Blood agar, chocolate agar.
- Selective media inhibit unwanted bacteria to recover specific pathogens. Enrichment media are liquid and also aid in pathogen recovery.
- Differential media are designed to display distinct colony appearances based on bacterial characteristics, often using dyes or substrates to differentiate species.
Examples of Differential Media
- Mannitol salts agar indicates mannitol fermentation, resulting in yellow colonies.
- Blood agar allows for classification based on hemolysis types: α, β, and γ.
- Mac Conkey agar distinguishes lactose fermenters, yielding pink colonies, while non-fermenters appear colorless.
- TCBS media are specifically for Vibrio cholerae, which produces yellow colonies through sucrose fermentation.
Transport Media
- Essential for transporting clinical specimens to prevent overgrowth of contaminants and preserve pathogen viability.
- Cary Blair transport medium and VR medium are commonly used for transporting stool samples from cholera suspects.
- Sach's buffered glycerol saline is utilized for transporting feces from patients suspected of bacillary dysentery.
- Pike's medium is another form of transport media employed for various specimens.
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Description
This quiz covers the classification of bacterial culture media based on consistency, composition, and purpose. Learn about solid, semisolid, and liquid media, along with synthetic and non-synthetic types. Test your knowledge on enriched media and their applications.