Bacteriology Lab 2: Culture Media

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Questions and Answers

What is the main purpose of using culture media in bacteriology labs?

To identify the cause of infection from clinical samples

To study the characteristics of microorganisms

To prepare biological products like vaccines and toxoids

All of the above (correct)

What is the most commonly used solidifying agent in solid media?

Peptone

Meat extract

NaCl

Agar (correct)

What is the main characteristic of semi-solid media?

They are liquid and used for bacterial separation

They are hard and used for bacterial growth

They are soft and used for demonstrating bacterial motility (correct)

They are complex and used for research purposes

What is the composition of Nutrient Broth (NB)?

Peptone, meat extract, and NaCl Signup and view all the answers

What is the purpose of using synthetic or defined media?

For research purposes and composition of every component is well known Signup and view all the answers

What is the difference between complex media and synthetic media?

Complex media have unknown composition, while synthetic media have known composition Signup and view all the answers

What is the main characteristic of liquid media?

They are liquid and bacteria grow uniformly producing general turbidity Signup and view all the answers

What is an example of a simple medium?

Nutrient broth Signup and view all the answers

What is the primary purpose of MacConkey agar?

To distinguish between lactose and non-lactose fermenters Signup and view all the answers

Which agar is used for the cultivation of pathogens from urine specimens and inhibits the swarming of Proteus sp.?

CLED agar Signup and view all the answers

What is the purpose of Stuart's medium?

To transport delicate organisms Signup and view all the answers

What should be done to prevent burning of agar during media preparation?

Heat and stir the mixture Signup and view all the answers

What is the purpose of covering the top of the flask or jar with aluminum foil during media sterilization?

To prevent contamination as the media cools Signup and view all the answers

What is the primary purpose of TCBS agar?

To isolate Vibrio cholerae and V. parahaemolyticus Signup and view all the answers

What is the purpose of XLD agar?

To recover Salmonella and Shigella species Signup and view all the answers

How much media should be poured into each petri plate during media preparation?

15-20 ml Signup and view all the answers

What is the main purpose of adding substances like blood, serum, or egg to a simple medium?

To grow bacteria that are exacting in their nutritional needs Signup and view all the answers

What is the purpose of adding vancomycin to Thayer Martin medium?

To kill most Gram-positive organisms Signup and view all the answers

What is the function of methylene blue in Eosin methylene blue medium?

To inhibit the growth of Gram-positive bacteria Signup and view all the answers

What is the purpose of Lowenstein-Jensen medium?

To grow Mycobacterium tuberculosis Signup and view all the answers

What type of media is used to recognize different bacteria based on their colony color?

Differential media Signup and view all the answers

What is the purpose of adding antibiotics to selective media?

To inhibit the growth of commensal or contaminating bacteria Signup and view all the answers

What is the purpose of using Blood agar?

To detect hemolysis Signup and view all the answers

What type of media is used to isolate Neisseria gonorrhoeae?

Thayer Martin medium Signup and view all the answers

Study Notes

Culture Media

Definition and Uses

Culture medium: food material or substances required for growing microorganisms in vitro
Uses:
- Identify the cause of infection from clinical samples for proper treatment
- Study characteristics or properties of microorganisms
- Prepare biological products like vaccines, toxoids, and antigens

Composition

Water
Energy source
Carbon source
Nitrogen source
Mineral salts
Special growth factors

Types of Culture Media

Classification Based on Physical State

Solid medium: agar is the most commonly used solidifying agent
Semi-solid medium: soft and useful in demonstrating bacterial motility and separating motile from non-motile strains
Liquid medium: also referred to as "broth", bacteria grow uniformly producing general turbidity (e.g., Nutrient broth)

Classification Based on Ingredients

Simple media: e.g., Nutrient broth, N. agar
Complex media: e.g., blood agar, ingredients difficult to estimate
Synthetic or defined media: specially prepared media from pure chemical substances for research purposes (e.g., peptone water)
Special media:
- Enriched media: add substances like blood, serum, or egg to simple medium (e.g., Blood agar, Chocolate agar)
- Selective media: inhibitory substances added to inhibit commensal or contaminating bacteria (e.g., Thayer Martin medium, Eosin methylene blue)
- Differential media: designed to recognize bacteria based on colony color (e.g., MacConkey agar, XLD agar)
- Transport media: used for transporting samples, delicate organisms may not survive without it (e.g., Stuart's medium, Buffered glycerol saline)
- Anaerobic media: used for growing anaerobic bacteria

Media Preparation

Assemble all chemicals in the work area
Accurately weigh each dry ingredient
Add distilled water to the correct volume
Heat and stir until all ingredients are in solution
Sterilize using the wet cycle (autoclave)

Media Sterilization

Sterilize by using the wet cycle (autoclave)
Cover the top of the flask or jar with aluminum foil
Line up sterile petri plates
Pour 15-20 ml of media into each petri plate
Keep the petri plate lid slightly open to prevent contamination

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Description

This quiz covers the basics of culture media in bacteriology, including its definition, importance, and uses in growing microorganisms outside the body.