Lab 4: Practical Microbiology in Dentistry

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Questions and Answers

What is the primary function of differential media in microbiology?

To provide a selective environment for specific bacteria
To inhibit the growth of unwanted bacteria
To allow multiple bacteria to grow with distinguishable colonial characteristics (correct)
To identify bacteria based on their hemolytic characteristics

Which of the following media is an example of a combination medium?

Blood agar
MacConkey agar
Nutrient agar
Mannitol salt agar (correct)

What characteristic of bacteria is observable on blood agar?

Gram staining
Hemolytic activity (correct)
Colony morphology
Motility

What is the primary advantage of using differential media in microbiology?

Preliminary characterization of bacteria (C) Signup and view all the answers

Which of the following statements is true about selective media?

They inhibit the growth of unwanted bacteria (A) Signup and view all the answers

What is the primary purpose of using combination media in microbiology?

To selectively grow specific bacteria while distinguishing between them (A) Signup and view all the answers

What is the primary function of phenol red in Mannitol salt agar?

To indicate a pH change due to mannitol fermentation (D) Signup and view all the answers

Which medium is used to differentiate between bacteria that ferment lactose and those that do not?

MacConkey agar (A) Signup and view all the answers

What is the purpose of thiosulfate in Sulfur indole motility (SIM) medium?

To detect the production of hydrogen sulfide gas (B) Signup and view all the answers

Which of the following media is used to detect the hydrolysis of urea to ammonia?

Urea broth (D) Signup and view all the answers

What is the primary function of intact red blood cells in Blood agar?

To facilitate the differentiation of hemolytic and non-hemolytic bacteria (C) Signup and view all the answers

Which medium is used to differentiate between bacteria that ferment sugars and those that do not?

Triple-sugar iron agar (B) Signup and view all the answers

What is the purpose of iron in Triple-sugar iron agar?

To detect the production of hydrogen sulfide gas (D) Signup and view all the answers

Which medium is used to differentiate between species of Staphylococcus?

Mannitol salt agar (D) Signup and view all the answers

What is the primary purpose of transport media in microbiology?

To preserve the viability of microorganisms in a specimen until processing (A) Signup and view all the answers

What is the role of salts in transport media?

To prevent the destruction of cells by enzymes (C) Signup and view all the answers

When would transport media be used in a microbiology laboratory?

When a specimen cannot be processed immediately (A) Signup and view all the answers

What is a characteristic of transport media?

It preserves the viability of microorganisms (B) Signup and view all the answers

What is the purpose of buffers in transport media?

To prevent the destruction of cells by enzymes (C) Signup and view all the answers

What is the result of using transport media in a microbiology laboratory?

The viability of microorganisms in a specimen is preserved (A) Signup and view all the answers

What is the primary purpose of enumeration media in microbiology?

To count the numbers of organisms in various samples (B) Signup and view all the answers

Which type of medium is used to grow anaerobic bacteria?

Reducing medium (D) Signup and view all the answers

What is the function of thioglycolic acid in reducing medium?

To absorb oxygen or slow the penetration of oxygen in the medium (C) Signup and view all the answers

What is the primary purpose of assay media in microbiology?

To test the effectiveness of antimicrobial drugs on microorganisms (D) Signup and view all the answers

What is the common feature of enumeration media and assay media?

They are both used to study microorganisms (B) Signup and view all the answers

What is the main difference between reducing medium and assay medium?

Reducing medium is used to grow anaerobic bacteria, while assay medium is used to test the effectiveness of antimicrobial drugs (D) Signup and view all the answers

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Study Notes

Differential Media

Allow multiple bacteria to grow but with distinguishable colonial characteristics.
Allow for preliminary characterization of bacteria.
Examples:
- Blood agar: a type of enriched medium that shows hemolytic characteristics of bacteria.
- Mannitol salt agar: selective and differential medium for Staphylococci.
- Other examples:
  - MacConkey agar: differentiates between bacteria that ferment lactose and those that do not.
  - Urea broth: differentiates between bacteria that hydrolyze urea to ammonia and those that do not.
  - Sulfur indole motility (SIM) medium: differentiates between H2S gas producers and non-producers.
  - Triple-sugar iron agar (TSIA): differentiates between fermentation of sugars, H2S production, and other characteristics.

Transport Media

Used when specimen cannot be processed immediately.
Preserve the viability of microorganisms in the specimen but do not allow growth.
Most transport media contain a salt and buffer to prevent destruction of cells by enzymes.

Other Media

Enumeration Media

Used to count the numbers of organisms in milk, water, food, soil, and other samples.

Assay Media

Used to test the effectiveness of antimicrobial drugs on the growth of microorganisms.

Reducing Media

Contains a substance (thioglycolic acid or cystine) that absorbs oxygen or slows the penetration of oxygen in a medium.
Important for growing anaerobic bacteria.

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