25 Questions
What is the purpose of the inhibitory substance in selective media?
To inhibit the growth of unwanted bacteria
What is the characteristic of differential media?
They contain an indicator that changes color when bacteria grow
Which of the following is an example of selective media?
Thayer Martin agar
What is the purpose of the acidic environment in some media?
To inhibit the growth of unwanted bacteria
Which of the following is an example of differential media?
Levinstein-Jensen medium
What is the purpose of blood agar?
To encourage the growth of bacteria
What type of bacteria can grow on blood agar?
Fastidious bacteria that may not grow on other media
What is a characteristic of interactive media?
They contain a pH indicator that changes color when bacteria grow
What is an example of an interactive medium?
Blood agar
What is the main difference between blood agar and other media?
It is enriched to support the growth of fastidious bacteria
What is the number of types of blood agar classified based on the hemolytic activity of bacteria?
Three
What is the type of hemolysis where the bacterial colony is surrounded by a clear zone?
Beta hemolysis
What is the characteristic of beta hemolysis?
Complete hemolysis
Which type of hemolysis is associated with the destruction of red blood cells?
Beta hemolysis
What is the classification of blood agar based on?
Hemolytic activity of bacteria
What is the main purpose of Mannitol Salt Agar?
To determine if the bacteria is halophilic and can ferment mannitol
What happens to the medium when Staphylococcus aureus ferments mannitol?
The medium turns yellow
What characteristic of Staphylococcus aureus is detected by Mannitol Salt Agar?
Its halophilicity and ability to ferment mannitol
What type of bacteria is Staphylococcus aureus?
Halophilic and mannitol-fermenting
Why is Mannitol Salt Agar used in the detection of Staphylococcus aureus?
Because it can detect the bacteria's halophilicity and ability to ferment mannitol
What is the main function of EMB agar?
To inhibit the growth of most Gram-negative bacteria
What is the primary role of methylene blue in EMB agar?
To indicate the pH level of the medium
What is the characteristic of EMB agar that makes it differential?
It indicates the acidity of the medium through a color change
What is the result of E. coli growth on EMB agar?
A green, metallic sheen
What type of bacteria is EMB agar primarily used to isolate?
Anaerobic bacteria
Study Notes
Microbiology Media
- Differential media contain an indicator that changes color when bacteria grow, e.g. Blood agar, MacConkey agar.
- Blood agar is an enriched, bacterial growth medium that encourages bacterial growth, especially for Streptococcus that may not grow normally in other media.
Types of Blood Agar
- Can be classified into three types based on hemolysis activity:
- Alpha (α) hemolysis (partial hemolysis)
- Beta (β) hemolysis (complete hemolysis), e.g. Staphylococcus aureus, which ferments mannitol and turns the medium yellow.
- Gamma (γ) hemolysis (no hemolysis)
Mannitol Salt Agar (MSA)
- Used to determine if bacteria are halophilic (salt-loving) and can ferment mannitol.
- Staphylococcus aureus ferments mannitol and turns the medium yellow.
Eosin Methylene Blue (EMB) Agar
- A selective and differential medium used to isolate coliform bacteria.
- Inhibits the growth of most Gram-positive bacteria.
- The methylene blue indicator shows the degree of acidity.
- If bacteria produce strong acid, such as E. coli, it leads to a greenish metallic color.
This quiz covers types of media used in microbiology lab, including selective and differential media, and their components.
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