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Intro to Microbio > Lab Exam 3 > Flashcards

Lab Exam 3 Flashcards

1
Q

What changes occur in Mannitol Salt Agar and Blood Agar for Staphylococcus aureus?

A

Mannitol Salt Agar: yellow zones mean Mannitol fermentation

Blood Agar: Beta hemolysis produces clear zones

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2
Q

What enzyme does the starch hydrolysis test detect?

A

Amylase.

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3
Q

What medium is used for the starch hydrolysis test?

A

Starch plate.

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4
Q

What is the reaction in the starch hydrolysis test?

A

Starch is broken down into sugar.

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5
Q

What visual cue indicates a positive starch hydrolysis test?

A

A clear zone after iodine flooding.

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6
Q

What enzyme does the casein hydrolysis test detect?

A

Caseinase.

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7
Q

What medium is used for the casein hydrolysis test?

A

Casein (milk) agar.

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8
Q

What is beta hemolysis?

A

complete lysis of red blood cells

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9
Q

how does beta hemolysis appear on Blood Agar?

A

clear zones

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10
Q

What visual cue indicates a positive casein hydrolysis test?

A

A clear zone around the colony.

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11
Q

What enzyme does the fat hydrolysis test detect?

A

Lipase.

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12
Q

What is the pH indicator in Mannitol Salt Agar, and what is the salt concentration?

A

pH indicator: phenol red
Salt concentration: 7.5%

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13
Q

What medium is used for the fat hydrolysis test?

A

Peanut oil agar with neutral red.

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14
Q

What visual cue indicates a positive fat hydrolysis test?

A

Red droplets around and under the colony.

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15
Q

What enzyme does the tryptophan hydrolysis test detect?

A

Tryptophanase.

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16
Q

What reagent is used in the tryptophan hydrolysis test?

A

Kovac’s reagent.

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17
Q

What visual cue indicates a positive tryptophan hydrolysis test?

A

A red/pink layer (ring) forms on top of the medium.

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18
Q

Identify each WBC

___________: multi-lobed nuclei ) 60-70%
___________: bi-lobed nuclei 20-25%
___________: lobed or irregular nucleus
___________: large, kidney-shaped or horseshoe-shaped nucleus
___________: large, round nucleus that occupies most of the cell

A

Neutrophil
Eosinophil
Basophil
Monocyte
Lymphocyte

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19
Q

What enzyme does the urea hydrolysis test detect?

A

Urease.

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20
Q

What visual cue indicates a positive urea hydrolysis test?

A

Bright pink color.

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21
Q

What pH indicator is used in the urea hydrolysis test?

A

Phenol red.

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22
Q

What three tests are included in the SIM test?

A

Sulfide, Indole, and Motility.

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23
Q

What medium is used for the SIM test?

A

SIM medium.

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24
Q

What indicates sulfide production in the SIM test?

A

Black precipitate.

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25
Q

What indicates indole production in the SIM test?

A

A red ring forms after adding Kovac’s reagent.

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26
Q

How is motility detected in the SIM test?

A

Diffuse growth away from the stab line.

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27
Q

What does the citrate utilization test detect?

A

Citrate metabolism.

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28
Q

What medium is used for the citrate utilization test?

A

Simmons Citrate Agar.

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29
Q

What visual cue indicates a positive citrate utilization test?

A

Blue color.

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30
Q

What enzyme does the phenylalanine deamination test detect?

A

Phenylalanase.

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31
Q

What reagent is used in the phenylalanine deamination test?

A

Ferric chloride.

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32
Q

What visual cue indicates a positive phenylalanine deamination test?

A

Dark green color.

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33
Q

What is the appearance of coliforms on Endo agar?

A

metallic sheen colonies

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34
Q

What is transformation?

A

The uptake of DNA from the environment.

35
Q

What is a plasmid?

A

Small circular DNA that gives bacteria extra traits, like antibiotic resistance.

36
Q

What process gives rise to fluorescent colonies?

A

Transformation with a plasmid.

37
Q

What is an antiseptic?

A

A chemical used on living tissues to reduce microbial load.

38
Q

What sugar is in the differential medium for detecting fecal coliforms?

A

Lactose

39
Q

What method tests sensitivity to antiseptics and disinfectants?

A

Disk diffusion method.

40
Q

At what temperature are fecal coliform cultures incubated?

A

44°C

41
Q

How do Staphylococci appear under a microscope?

A

Cocci in clusters.

42
Q

What is the purpose of Mannitol Salt Broth?

A

To enrich for staphylococci by selecting for salt-tolerant species.

43
Q

What is the purpose of Mannitol Salt Agar?

A

differentiate species based on mannitol fermentation.

44
Q

What is the pH indicator in Mannitol Salt Agar?

A

Phenol red.

45
Q

Why is Bergey’s Manual important?

A

most important single source of information for bacterial identification

46
Q

What visual cue indicates S. aureus on Mannitol Salt Agar?

A

Yellow colonies and agar.

47
Q

What test confirms pathogenic S. aureus?

A

Coagulase test.

48
Q

What visual cue indicates a positive coagulase test?

A

Plasma coagulates into a gel.

49
Q

What bacteria are used in yogurt production?

A

L. bulgaricus and S. thermophilus.

50
Q

How are antibiotics tested for sensitivity?

What agar is used?

A

Using Kirby-Bauer disk diffusion method and placing paper disks on lawn of bacteria

Mueller-Hinton Agar

51
Q

What ingredients are needed to make yogurt?

A

Milk and a starter culture.

52
Q

Is yogurt acidic or alkaline?

A

Acidic.

53
Q

What is the difference between an antimicrobial and an antibiotic?

A

Antimicrobials: target, kill, or inhibit growth of all microorganisms

Antibiotics: ONLY target bacteria

54
Q

What is the mechanism of action of Penicillin and Ampicillin?

A

Disruption of cell wall synthesis.

55
Q

What is the mechanism of action of Tetracycline, Erythromycin, and Streptomycin?

A

Disruption of protein synthesis

56
Q

Which antibiotic is effective only against Gram-positive bacteria?

A

Penicillin

57
Q

What is Durham Tube Sugar Fermentation testing for?

A

Fermentation of sugar w/ acid production and gas production.

58
Q

What media is used in Durham Tube Sugar Fermentation?

A

Phenol red broth with sugar and a Durham tube

59
Q

What reaction is being tested in Durham Tube Sugar Fermentation?

A

Sugar fermentation producing acid and/or gas.

60
Q

What pH indicator is used in Durham Tube Sugar Fermentation?

A

Phenol red

61
Q

What is the visual cue for positive/negative results in Durham Tube Sugar Fermentation?

A

Yellow= acid production (+)

Bubble in the Durham tube= gas production.

No color change= negative (-)

62
Q

What is the Methyl Red Test testing for?

A

Mixed acid fermentation

63
Q

What media is used for the Methyl Red Test?

A

MR-VP broth

64
Q

What reaction is being tested for the Methyl Red Test?

A

stable acidic end-products from glucose fermentation.

65
Q

What pH indicator is used?

A

Methyl red reagent

66
Q

What is the visual cue for positive/negative results?

A

Red =a positive result
yellow = a negative result.

67
Q

What is the Voges-Proskauer Test testing for?

A

Production of acetoin from glucose fermentation.

68
Q

What media & reagents is used for the Voges-Proskauer test?

A

Media: MRVP broth
Reagents: alpha-napthol & KOH

69
Q

What reactions are tested in the Voges-Proskauer test?

A

acetoin production from glucose fermentation and its conversion to diacetyl in the presence of Barritt’s reagents.

70
Q

What are the visual cues and pH indicators in the Voges-Proskauer test?

A

red color = positive (+)
No color change = (-)

71
Q

What is the purpose of the catalase test?

A

identify organisms that produce the enzyme catalase

72
Q

What media is used for the catalase test?

A

No specific media is used; the test is performed directly on a slide or agar plate

73
Q

What enzymes and reactions are tested in the catalase test?

A

detects catalase, an enzyme that converts hydrogen peroxide into water and oxygen gas

74
Q

What are the visual cues in the catalase test?

A

Bubbling = positive (+)
No rxn = negative (-)

75
Q

What is the purpose of the oxidase test?

A

determine if an organism produces cytochrome c oxidase, an enzyme involved in the electron transport chain

76
Q

What media is used for the oxidase test?

A

No specific media is required;
filter paper or a swab with oxidase reagent.

77
Q

What enzymes and reactions are tested in the oxidase test?

A

cytochrome c oxidase, which transfers electrons to oxygen during aerobic respiration

78
Q

What are the visual cues in the oxidase test?

A

purple or dark blue color change within 20 seconds

79
Q

What is the purpose of the Gelatin Hydrolysis test?

A

to see if an organism produces gelatinase, an enzyme that hydrolyzes gelatin

80
Q

What media is used for the gelatin test?

A

Nutrient gelatin

81
Q

What enzymes and reactions are tested in the gelatin test?

A

presence of gelatinase, which breaks down gelatin into its constituent amino acid

82
Q

What are the visual cues in the gelatin test?

A

There will be a clear zone around a colony that produces
gelatinase.

83
Q

How do you distinguish between Staphylococcus and Streptococcus in terms of catalase test?

A

Staph is catalase positive, while Strep is catalase negative.

84
Q

In citrate test, Simmons citrate medium contains citrate and the pH indicator?

A

bromocresol green.

Intro to Microbio (16 decks)

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