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 both enzymes are present and they completed the reaction

B nitrate reductase is the only enzyme present

C nitrite reductase is the only enzyme present

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

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

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

D add Barritt’s A & B 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 more than one of the choices are correct

B Kovac’s reagent

C Barritt’s A & B

D phenol red

E zinc

F none of these are correct

Question #4

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

A inhibit Gram positive organisms

B complete the chemical reaction

C differential fermenters from non-fermenters

D activate the substrate

E inhibit Gram negative organisms

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 negative for growth and positive for fermentation

B positive for growth and negative for fermentation

C positive for growth and positive for fermentation

D negative 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 identify halophiles

C inhibit Gram positive organisms

D inhibit Gram negative organisms

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 organismâ s enzyme

B indicate the completion of the reaction

C activate the substrate

D complete the chemical reaction

Question #8

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

A inhibit Gram negative orgnaisms

B differential fermenters from non-fermenters

C inhibit Gram positive organisms

D complete the chemical reaction

E activate the substrate

Question #9

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

A indicate the completion of the reaction

B activate the organismâ s enzyme

C differential fermenters from non-fermenters

D complete the chemical reaction

E activate the substrate

Question #10

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

A glucose

B lactose

C tryptophan

D sucrose

E citrate

Question #11

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

A acid

B oligonucleotides

C alcohol

D lipids

E carbohydrates

Question #12

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

A starch

B sucrose

C lactose

D maltose

E glucose

Question #13

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

A sucrose

B glucose

C none of these

D starch

E lactose

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 Kovac’s reagent

B methyl red

C Vogues-Proskauer

D Barritt’s A& B

Question #15

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

A epsilon hemolysis

B alpha hemolysis

C gamma hemolysis

D beta hemolysis

Question #16

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

A all of these

B none of these

C starch

D sucrose

E lactose

F glucose

Question #17

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

A lipids

B carbohydrates

C alcohols

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 traps gas bubbles

B makes the pH alkaline

C makes the pH acidic

D prevents 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 excrete an enzyme that degrades protein.

B the bacteria are alpha-hemolytic.

C the bacteria are beta-hemolytic.

D the bacteria excrete acid.

E the bacteria are gamma-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 alpha-hemolytic.

B the bacteria are beta-hemolytic.

C the bacteria excrete an enzyme that degrades protein.

D the bacteria excrete acid.

Question #21

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

A Staphylococcus aureus

B Streptococcus pyogenes

C Micrococcus luteus

D Staphylococcus epidermidis

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 glucose

D it was inhibited by bile

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 Spirit Blue Agar

B Coagulase

C Bile Esculin Agar

D DNase Agar

E Columbia CNA

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 used to treat only Gram-positive bacterial infections

C they are only used to treat spirilla bacteria

D they are used to treat Gram-positive and Gram-negative 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 therapeutic level

B mode of action

C spectrum of activity

D selective toxicity

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