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Lab Exam Flashcards

(97 cards)

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1
Q

What do molecular methods of microbial identification rely on

A

distinctive features microbial nucleic acids for identification

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2
Q

What does serological methods of microbial identification rely on

A

recognition of microbial features by antibody proteins; based on the use of blood serum

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3
Q

What can antibody-based methods of microbe recognize

A

individual features on microbial cells called antigens

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4
Q

What does mass spectroscopy methods identify microbes based on

A

most abundant proteins in the cells

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5
Q

What are tests that help identify chemoheterotrophic bacteria

A

gram stain
motility
oxygen relationship
glucose fermentation
catalase
oxidase

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6
Q

What does the glucose fermentation test detect

A

whether the microbe can grow in the medium and if it can ferment glucose

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7
Q

What does a tube of carbohydrate fermentation broth contain that is the target component of the medium

A

specific sugar as a potentially fermentable carbon and energy source

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8
Q

What does brom-cresol purple do in glucose fermentaiton broth

A

changes to a yellow color as a result of the considerable acid production from fermentative breakdown of the sugar

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9
Q

What percent of gas is considered a positive result

A

10

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10
Q

What does the nitrate reduction test detect

A

whether the microbe can grow on the medium supplied using anaerobic respiration with nitrate as the final electron acceptor

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11
Q

What is the target component in the medium for nitrate reduction test

A

potassium nitrate

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12
Q

With the use of a durham tube in the medium reduction of nitrate to _______ or _____________ can be detected

A

nitrite; nitrogen gas

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13
Q

What do you look for to observe reduction of nitrate to nitrogen gas

A

large bubble in durham tube

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14
Q

What is the complete reduction of nitrate to n gas

A

denitrification

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15
Q

To test for reduction of nitrate to nitrite what do you need to add to the test tube and mix? what do you look for upon mixing

A

nitrite reagents (sulfanilamid and N-ethylenediamine); pink or red color

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16
Q

If you see no red in the test of reduction from nitrate to nitrite what do you do

A

add a few more drops of each reagent, mix well, and observe again

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17
Q

How do we check for unreduced nitrate

A

adding a small amount of granulated zinc to any tube not showing a positive reaction for nitrite or gas

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18
Q

If nitrate is present what will it look like

A

be reduced by the zinc to nitrite which will react with the reagents already added forming a pink or red color so it is negative for the reaction

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19
Q

Motility test detects

A

microbes that are motile with flagella can usually swim through a semi-solid medium containing a small amount of agar

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20
Q

How much agar is in the motility test

A

0.4

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21
Q

What is the target in the medium for motility

A

agar

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22
Q

What does the catalase test for

A

enzyme catalase present

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23
Q

what does catalase do

A

breakdown of toxic hydrogen peroxide

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24
Q

What type of respiring microbes would possess catalase

A

stric aerobes or facultative anaerobes

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25
What is the hydrogen peroxide breakdown
2H2O2 --> 2H2O + O2
26
Prior to catalase how are the grown
on a slant or plate of an al purpose medium
27
What percent of hydrogen peroxide is added for the catalase test
3-5%
28
What type of reaction is the oxidase test
colorimetric reaction
29
What is oxidase testing for
cytochrome C oxidase enzyme in the respiratory electron transport chain
30
what color will the plastic strips turn when the oxidase test is positive
purple
31
T/F you must look for an immediate response to the oxidase test
T
32
The enterobacteriaceae is a family of gram ______ __________
negative proteobacteria
33
All enteric are... gram stain shape
gram negative rods
34
When are enteric bacteria mistaken for cocci
in older cultures as cells shorten up to a coccobaccilus shape
35
All enteric are... _______heterotroph respiration
chemoorganoheterotrophic true facultative anaerobes
36
Are enterics able to ferment glucose
yes
37
All enteric are... catalase oxidase
positive negative
38
T/F most enteric are motile
T
39
The KIA test is used only for gram _____ bacteria mainly enterics and pseudomonas
negative
40
What is the purpose of KIA test
test fermentation of a major sugar (lactose) and a minor sugar (glucose) as well as production of hydrogen sulfide
41
What is the purpose of the methyl red test
the purpose of this test is to identify the end products from glucose fermentation
42
what does the voges proskauer test indicate
the neutral products formed by the butanediol
43
generally enterics are positive for the MR or the VP test but not
both
44
What is the color for MR test that is postive and what does it mean
red; mixed acid fermentation; pH has dropped and then remained below 4.4
45
What is the color for a negative MR test and what does it mean
yellow; indicative of butanediol fermentation; pH has dropped and then risen to 6.2 or above
46
What is the purpose of the simmons citrate test
test for the use of citrate as a carbon and energy source
47
What is the target component in the medium simmons citrate test
sodium citrate
48
If citrate has been used....
an alkaline reaction results and turns bright blue
49
What medium is known to give false positive when there is too-heavy innoculation
simmons citrate agar
50
what does emb agar inhibit
growth of gram positive bacteria due to eosin and methylene blue dyes
51
What gram bacteria is typically used on EMB
negative
52
Can EMB be used to identify lactose fermenting bacteria
yes
53
Is EMB both differential and selective
yes
54
What will a coli type look like on EMB
colonies appear dark, and have bright green metallic sheen if observed by reflected light
55
Why does a sheen result
rapid fermentation of lactose, causing a low pH to precipitate methylene bue
56
What will a aerogenes type look like on EMB
colonies appear less dark; normally light colored with mucoid rim surrounds a dark center
57
What do non lactose fermenting microbes look like on EMB
light
58
What is the purpose of the phenylaline test
test for the deamination of the AA phenylalanine
59
if phenylalanine deamination has taken place, the reagent will react with the phenyl pyruvic acid formed and turn what color
dark green
60
What does MIO test
motility ability to produce indole ability to decarboxylate ornithine
61
how do bacteria produce indole, pyruvic acid, and ammonia
produce the enzyme tryptophan's and degrade tryptophan
62
What is in kovac's reagent
p-dimethylaminobenzoladhyde, butanol, and hydrochloric acid
63
What color is produced in MIO when there is a reaction with indole
red color
64
indole is detected in MIO by its reaction
with the chemicals in kovac's reagent
65
How to test for ornithine decarboxylation in MIO
observe the lower 3/4 (anaerobic region) of the medium for change in color of the pH indicator; growth must be present in this part of the tube
66
What color will be present in ornithine decarboxylation of MIO when there is a positive reaction
gray, blue, purple
67
decarboxylation of lysine, ornithine, and histidine will result in production of
cadaverine, putrescine, and histamine
68
What is a negative reaction for lysine decarboxylase broth
yellow color
69
What is a positive reaction for lysine decarboxylase and what it means
gray, blue, purple--alkaline product that neutralizes the acid produced from glucose fermentation
70
will a strict aerobe such as pseudomonas grow in decarboxylase control test
no it will remain purple
71
What does the lactose fermentation test detect
whether the microbe can grow in the medium; and if so, if it can ferment lactose
72
What is the target component in lactose fermentation broth
lactose
73
What color change occurs if the lactose fermentation broth is positive
purple to yellow
74
What do multitest systems provide savings in terms of
time and reagents used
75
What number of multi test identification is used for enteric bacteria
20E
76
If the methyl red results are yellow what does it mean
negative reaction and has butanediol fermentation
77
If the methyl red results are orange what does it mean
equivocal reaction
78
How long must MR test incubate
about 2 days
79
How long must KIA be incubated
24 hours only
80
What type of medium is EMB
differentail and selective
81
What is the selevtive part of EMB
eosin and methylene blue dyes
82
What is the differentail part of EMB
lactose
83
How long must you incubate EMB
only 24 hours
84
What type of lactose bacteria will look fisheye on EMB
aerogenes type
85
How do you innoculate the phenylalanine test
streak across top of the penylalanine agar slant only
86
What does a dark green color appearing on the slant of a phenylalalinine test mean
phenylalanine deamination has occurred the reagent will react with the phenylpyruvic acid formed
87
How do you inoculate the MIO agar
stab the medium about 3/4 the depth of the tube
88
What reagent must be added to the test tube to determine if phenylalnine deamination ahs occured
FeCl3
89
If the bottom 3/4 (anaerobic region) is yellow in the MIO what does it mean
glucose fermentation occured
90
To determine indole production in MIO what must be added
kovacs reagent
91
Where is it best to detect formation of highly alkaline diamine
anaerobic growth region of the medium
92
What type of microbe will not grow in the decarboxylase control test
pseudomonas--a strict aerobe
93
What does pseudomonas look like in the decarboxylase broth
purple
94
Define obligate aerobic
requires oxygen
95
Define microaerophile
requires low levels of oxygen
96
Define facultative respirer
can grow with or without oxygen
97
Define obligate anaerobic respirer
oxygen free

Microbiology (29 decks)

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