Lab Exam 2

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Question #1

You are conducting the nitrate reduction test. After incubating your bacterium and adding alpha naphthylamine and sulfanilic acid to the potassium nitrate (KNO3) broth, there is no color change. After adding zinc powder, the broth color becomes red in color. Which of the following interpretations of this result is the correct one?

A nitrate reductase is the only enzyme present

B nitrite reductase is the only enzyme present

C both enzymes are present and they completed the reaction

D neither nitrate nor nitrite reductase are present

Question #2

You are conducting the nitrate reduction test. After incubating your bacterium and adding alpha naphthylamine and sulfanilic acid to the potassium nitrate (KNO3) broth, there is no color change. According to our lab protocol, what is the next step in order to complete this test?

A add Barritt’s A & B and wait a few minutes to see if the color changes

B add more alpha naphthylamine and sulfanilic acid because it did not work

C add Kovac’s reagent and wait a few minutes to see if the color changes

D add zinc and wait a few minutes to see if the color changes

Question #3

Which of the following compounds is an indicator used in the nitrate reduction test?

A zinc

B Kovac’s reagent

C more than one of the choices are correct

D phenol red

E none of these are correct

F Barritt’s A & B

Question #4

Mannitol is an ingredient in Mannitol Salt Agar. The purpose of mannitol in this medium are:

A activate the substrate

B differential fermenters from non-fermenters

C inhibit Gram negative organisms

D inhibit Gram positive organisms

E complete the chemical reaction

Question #5

If Mannitol Salt agar shows white bacterial colonies and the agar is PINK in color, which of the following statements about the bacteria growing on the agar is correct? They are:

A positive for growth and positive for fermentation

B negative for growth and negative for fermentation

C negative for growth and positive for fermentation

D positive for growth and negative for fermentation

Question #6

Sodium chloride is an ingredient in Mannitol Salt Agar. The purpose of sodium chloride in this medium are:

A differential fermenters from non-fermenters

B inhibit Gram negative organisms

C inhibit Gram positive organisms

D identify halophiles

E more than one of the choices are correct

Question #7

Neutral red is a MacConkey’s ingredient. The purpose of neutral red in this medium is to:

A activate the substrate

B indicate the completion of the reaction

C complete the chemical reaction

D activate the organismâ s enzyme

Question #8

Bile salt is a MacConkey’s ingredient. The purpose of bile salt in this medium is:

A complete the chemical reaction

B activate the substrate

C differential fermenters from non-fermenters

D inhibit Gram negative orgnaisms

E inhibit Gram positive organisms

Question #9

Lactose is a MacConkey’s ingredient. The purpose of lactose in this medium is:

A activate the substrate

B differential fermenters from non-fermenters

C activate the organismâ s enzyme

D complete the chemical reaction

E indicate the completion of the reaction

Question #10

From the IMVIC test series, which of the following is the differential agent found in the Citrate test?

A sucrose

B glucose

C tryptophan

D lactose

E citrate

Question #11

From the IMVIC test series, which of the following is a general product from the Voges-Proskauer reaction?

A oligonucleotides

B alcohol

C carbohydrates

D lipids

E acid

Question #12

From the IMVIC test series, which of the following is the differential agent found in the Methyl Red test?

A starch

B maltose

C lactose

D glucose

E sucrose

Question #13

From the IMVIC test series, which of the following is the selective agent found in the Methyl Red test?

A lactose

B glucose

C none of these

D sucrose

E starch

F all of these

Question #14

From the IMVIC test series, which of the following is the indicator used in the Methyl Red reaction?

A Barritt’s A& B

B Kovac’s reagent

C Vogues-Proskauer

D methyl red

Question #15

Which type of hemolysis cause complete hemolysis with completely clear zone around bacterial growth?

A alpha hemolysis

B gamma hemolysis

C beta hemolysis

D epsilon hemolysis

Question #16

From the Carbohydrate test series, which of the following is the selective agent found in the Carbohydrate tests?

A none of these

B glucose

C starch

D all of these

E lactose

F sucrose

Question #17

From the Carbohydrate test series, which of the following is a general product from these reactions?

A alcohols

B lipids

C carbohydrates

D oligonucleotides

E acids

Question #18

From the Carbohydrate test series, what is the purpose of the Durham tube used in the three carbohydrate reactions?

A makes the pH acidic

B makes the pH alkaline

C prevents gas bubbles

D traps gas bubbles

Question #19

You streak an unknown bacterium on a Blood Agar Plate. After incubation, you notice that the bacteria grew, but despite the growth, the red color typical of this medium was UNCHANGED. Which of the following statements about the bacteria growing on the agar is correct?

A the bacteria are alpha-hemolytic.

B the bacteria are gamma-hemolytic.

C the bacteria excrete an enzyme that degrades protein.

D the bacteria excrete acid.

E the bacteria are beta-hemolytic.

Question #20

You streak an unknown bacterium on a Blood Agar Plate. After incubation, you notice a distinct zone around the colonies that is OLIVE GREEN in color. Which of the following statements about the bacteria growing on the agar is correct?

A the bacteria are beta-hemolytic.

B the bacteria excrete acid.

C the bacteria are alpha-hemolytic.

D the bacteria excrete an enzyme that degrades protein.

Question #21

Which of the following Gram-positive, catalase-positive organisms secrete beta hemolysin?

A Streptococcus pyogenes

B Staphylococcus epidermidis

C Micrococcus luteus

D Staphylococcus aureus

Question #22

Suppose you inoculated your Bile Esculin Agar plate with Streptococcus pyogenes. After incubation, you observe no growth on the Bile Esculin Agar plate. Which of the following is the BEST explanation for this observation?

A it was inhibited by ferric ammonia citrate

B it was inhibited by esculin

C it was inhibited by bile

D it was inhibited by glucose

Question #23

Suppose you had a pure bacterica culture. You believe that it is either Streptococcus pyogenes or Enterococcus durans. Which of the following biochemical tests would help you determine which of these two species you had?

A Bile Esculin Agar

B Columbia CNA

C DNase Agar

D Coagulase

E Spirit Blue Agar

Question #24

Which of the following statements concerning broad spectrum antibiotics is TRUE?

A they are used to treat only Gram-negative bacterial infections

B they are only used to treat spirilla bacteria

C they are used to treat Gram-positive and Gram-negative bacterial infections

D they are used to treat only Gram-positive bacterial infections

Question #25

Which of the following terms refers to the ability of an antimicrobial drug to harm the target microbe without harming the host?

A spectrum of activity

B therapeutic level

C selective toxicity

D mode of action

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