Question 1

What are the main components of eosin methylene blue agar?

Accepted Answer

Eosin Y, methylene blue, lactose, and peptone.

Answer

Xylose, phenol red, lactose, and beef extract.

Answer

Agar, thaumatin, glucose, and tryptone.

Answer

Eosin Y, methylene blue, galactose, and casein.

Answer

Crystal violet, malachite green, sucrose, and yeast extract.

Question 2

What type of bacteria does eosin methylene blue agar inhibit (prevents the growth of)?

Accepted Answer

Gram-positive bacteria.

Answer

Dermatophyte fungi.

Answer

Gram-negative bacteria.

Answer

Acid-fast bacteria.

Question 3

What is the function of eosin Y and methylene blue in eosin methylene blue agar?

Accepted Answer

To inhibit Gram-positive bacteria and differentiate lactose fermenting bacteria.

Answer

To identify antibiotic resistance genes and promote the growth of Gram-positive bacteria.

Answer

To enhance the growth of Gram-negative bacteria and visualize fungal colonies.

Answer

To differentiate Gram-negative bacteria and inhibit the growth of non-lactose fermenting bacteria.

Question 4

What is the purpose of using eosin methylene blue agar in the identification of Escherichia coli?

Accepted Answer

To differentiate E. coli from other lactose fermenting bacteria based on colony coloration and sheen.

Answer

To identify specific genetic markers of E. coli.

Answer

To visualize the morphology of E. coli colonies under a microscope.

Answer

To enhance the growth of E. coli in culture media.

Answer

To inhibit the growth of E. coli and promote the growth of other bacteria.

Question 5

What is the purpose of eosin methylene blue agar in the differentiation of coliform bacteria?

Accepted Answer

To distinguish between coliform and non-coliform bacteria based on their ability to ferment lactose.

Answer

To visualize the formation of pseudohyphae in yeast colonies.

Answer

To selectively inhibit the growth of filamentous fungi.

Answer

To identify the presence of antibiotic-resistant bacteria.

Answer

To differentiate between Gram-positive and Gram-negative bacteria.

Question 6

What is the function of lactose in eosin methylene blue agar?

Accepted Answer

To serve as a carbohydrate for fermentation.

Answer

To inhibit the growth of Gram-negative bacteria.

Answer

To facilitate the growth of Gram-positive bacteria.

Answer

To visualize fungal colonies.

Answer

To differentiate between different types of agar.

Question 7

What is the purpose of eosin methylene blue agar in microbiology?

Accepted Answer

To selectively isolate and differentiate lactose fermenting bacteria.

Answer

To identify antibiotic resistance genes.

Answer

To enhance the growth of Gram-positive bacteria.

Answer

To visualize fungal colonies.

Question 8

If I have a colony that grows on EMB (Eosin Methylene Blue) agar but it does not have any color, what does this mean?

Accepted Answer

The bacteria is gram-negative but CANNOT ferment lactose.

Answer

The bacteria is gram positive

Answer

The bacteria CAN ferment lactose (use lactose for energy)

Answer

The bacteria is both gram negative and CAN ferment lactose (use lactose for energy)

Question 9

On an EMB agar, a mild fermenter (eater) of lactose produces a fainter color, whereas a strong fermenter will produce a bright almost glowing color.

Accepted Answer

TRUE

Answer

FALSE

Question 10

What is the purpose of using Columbia Blood Agar in microbiology?

Accepted Answer

To cultivate fastidious bacteria and differentiate them based on their hemolytic (hemolysis) activity.

Answer

To test bacterial susceptibility to disinfectants.

Answer

To check for antibiotic resistance in bacteria.

Answer

To identify the presence of certain types of bacterial toxins.

Question 11

What is the composition of Columbia Blood Agar?

Accepted Answer

Enzymatically digested animal tissue, peptones, yeast extract, and sheep blood.

Answer

Lactose, glucose, agar, and sheep blood.

Answer

Soy protein, yeast extract, and human blood.

Answer

Glucose, tryptone, agar, and bovine blood.

Question 12

Which type of hemolysis is characterized by complete lysis of red blood cells on Columbia Blood Agar?

Accepted Answer

Beta-hemolysis

Answer

Delta-hemolysis

Answer

Gamma-hemolysis

Answer

Alpha-hemolysis

Question 13

What is the primary function of Columbia Blood Agar in clinical microbiology?

Accepted Answer

To isolate and identify pathogenic bacteria from clinical samples since the ability to destroy red cells is indicative of a deadly infection

Answer

To test the efficacy of disinfectants on bacteria.

Answer

To differentiate bacterial species based on their motility.

Answer

To determine the antibiotic susceptibility of bacteria.

Question 14

What is the main differential component added to Columbia Blood Agar to identify bacteria that produce hydrogen sulfide?

Accepted Answer

Sodium thiosulfate

Answer

Potassium nitrate

Answer

Lactose

Answer

Xylose

Question 15

Which of the following bacteria are betahemolytic?

Accepted Answer

Streptococcus pyogenes (strep throat)

Answer

Staphylococcus aureus

Answer

Escherichia coli

Answer

Salmonella enterica

Question 16

What is the main difference between beta hemolytic, alpha hemolytic, and nonhemolytic bacteria?

Accepted Answer

Their ability to break down red blood cells

Answer

Their size

Answer

Their shape

Answer

Their color

Question 17

What characterizes nonhemolytic bacteria in terms of their effect on red blood cells?

Accepted Answer

They do not break down red blood cells

Answer

They cause complete breakage of red blood cells

Answer

They cause partial breakage of red blood cells

Answer

They change the color of red blood cells

Question 18

Which type of hemolysis is characterized by a zone of incomplete lysis (partial lysis/breakdown) around bacterial colonies?

Accepted Answer

Alpha hemolysis

Answer

Nonhemolysis

Answer

Both of the above

Answer

Beta hemolysis

Question 19

Which of the following is a characteristic of beta hemolytic bacteria?

Accepted Answer

They cause complete lysis of red blood cells

Answer

They cause partial lysis of red blood cells

Answer

They do not affect red blood cells

Answer

They change the shape of red blood cells

Question 20

Which type of hemolysis is characterized by no visible effect on red blood cells?

Accepted Answer

Nonhemolysis

Answer

All of the above

Answer

Alpha hemolysis

Answer

Beta hemolysis

Question 21

Which type of hemolysis is characterized by a greenish discoloration around bacterial colonies?

Accepted Answer

Alpha hemolysis

Answer

Both of the above

Answer

Beta hemolysis

Answer

Nonhemolysis

Question 22

What is the purpose of using nalidixic acid in Columbia CNA Blood agar?

Accepted Answer

To inhibit the growth of gram-negative bacteria.

Answer

To promote the growth of gram-negative bacteria.

Answer

To differentiate between different species of gram-positive bacteria.

Answer

To assess antibiotic susceptibility in gram-negative bacteria.

Question 23

Which of the following is a selective ingredient commonly found in Columbia CNA agar media?

Accepted Answer

Nalidixic acid.

Answer

Erythromycin.

Answer

Gentamicin.

Answer

Tetracycline.

Question 24

What is the primary purpose of using Columbia CNA media?

Accepted Answer

To isolate and detect gram-positive bacteria.

Answer

To differentiate between different species of gram-negative bacteria.

Answer

To isolate and detect gram-negative bacteria.

Answer

To assess antibiotic susceptibility in gram-negative bacteria.

Question 25

What is the distinguishing feature of Columbia blood agar compared to other types of agar?

Accepted Answer

It contains colistin and nalidixic acid to inhibit gram negative bacteria

Answer

It is used for identifying viruses

Answer

It is a selective medium

Answer

It is made from beef extract

Question 26

What color does Columbia blood agar typically turn after the growth of bacteria?

Accepted Answer

Red

Answer

Purple

Answer

Green

Answer

Yellow

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