LAB FINAL Flashcards
1
Q
What is needed on every plate?
A
Name
Instructor’s name
Date
Name of organism
2
Q
For sterilizing wire loops, what color must the flame be?
A
blue
3
Q
Why should you let a hot loop cool after flaming before picking up the organism?
A
A hot loop will kill the cells
4
Q
What is the first step in transferring from one medium to a second sterile medium?
A
Check to make sure the organism you’re transferring is the correct one
5
Q
T/F:
Always place a cap directly on the table face up to prevent contamination
A
False
6
Q
T/F:
Always incubate the plates taped together and upside down
A
TRUE
7
Q
What is the purpose of quadrant streaking?
A
To obtain isolated colonies from an inoculum
8
Q
What materials are needed for quadrant streaking?
A
inoculum
agar plates
inoculating loops
propane tanks
9
Q
How many quadrants are there in quadrant streaking?
A
4….duh.
10
Q
How long is the incubation for a quadrant streaked plate?
A
24 hours
11
Q
What type of growth is seen in the 4th quadrant?
A
single colonies
12
Q
What type of growth is seen on the 2nd quadrant?
A
dense growth
13
Q
What solution should you use to disinfect your work station?
A
70% ethanol
10% bleach
14
Q
How should solid waste be disposed?
A
placed in a biohazard bag
and autoclaved
before being thrown out with the regular trash
15
Q
What is the purpose of aseptic technique?
A
prevent environmental contamination
maintain pure stock cultures
isolation of a single species from a mixed culture
prevent lab microbes from being released into environment
16
Q
What are the 3 plating techniques?
A
pouring plate
spreading plate
streaking plate
17
Q
What is TSA (trypticase soy agar) used for?
A
general purpose medium allowing for a variety of organisms to grow
18
Q
What is blood agar used for?
A
To grow fastidious organisms
and
differentiate bacteria based on hemolytic properties
19
Q
What is MacConkey agar used for?
A
Grow gram negative bacteria
and
differentiate lactose from non-lactose fermenters
20
Q
What color are lactose fermenters on MacConkey agar?
A
red/pink
21
Q
What color are non-lactose fermenters on MacConkey agar?
A
white/colorless
22
Q
What is the purpose of Hektoen enteric agar?
A
differentiate *Salmonella *and *Shigella *from enteric bacteria
23
Q
What causes green, moist, raised colonies on Hektoen enteric agar
A
Shigella
24
Q
On Hektoen enteric agar, what causes blue-green colonies with or without black centers?
A
Salmonella
25
What bacteria is Brilliant Green agar selective for?
*Salmonella*
26
What color is Salmonella on XLD (Xylose Lysine Deoxycholate) agar?
red colonies with a black center
27
What color are E. coli colonies on Eosin Methylene Blue agar?
metallic sheen
28
What is another name for the iodine in gram staining?
mordant
29
What are the steps (in order) of gram staining?
Crystal Violet
Iodine
Decolorizer
Safranin
(CIDS)
30
What is the most critical step of gram staining?
Decolorizer
31
T/F:
Gram positive bacteria stain pink/ red with gram staining
false -- gram positive bacteria stain purple/ blue
32
How does heat fixing occur with gram staining?
Pass slide over open flame 3x
33
When should you stop adding decolorizer?
When the runoff becomes clear
or after
10-20 seconds
34
What power on the microscope should be used to look at gram stained samples?
100x (oil)
35
T/F Bacilli come in clusters, chains, pairs, and tetrads
FALSE
COCCI come in clusters, chains, pairs, or tetrads
36
What is the purpose of the oxidase test?
Used to ID bacteria that produce
## Footnote
*cytochrome oxidase*
37
T/F
you should always mark delayed reactions in an oxidase test
FALSE
delayed reactions should always be ignored
38
T/F:
A positive oxidase test changes colors to dark purple
TRUE
39
What is the purpose of the catalase test?
detects the enzyme catalase that converts hydrogen peroxide to water and gaseous oxygen
40
T/F catalase activity is present in obligate anaerobic bacteria
false -- catalase activity is present in most aerobic bacteria but not in obligate anaerobes
41
What is indicative of a positive catalase test?
immediate bubbling
42
T/F Anaerobes are oxidase negative
TRUE
43
What are the possible results in a motility test?
positive
negative
uninoculated
44
What is the medium for a Urease test?
Christenson medium
45
What does a positive Indole test look like?
reagent layer (on the top) is a deep red, remainder is clear
46
What is tested for in a Methylene Red test?
small molecular weight acids
47
What color is a positive Methylene Red test?
red
48
What is being tested for in a Voges-Proskauer test?
Acetoin derived from glucose
49
What color is positive in a Voges-Proskauer test?
red
50
What is tested for in a Simmons citrate test?
ability to use citrate as a sole carbon source
51
What color is positive on a Simmons citrate test?
blue
52
What is API 20E?
standardized identification system for enterobactericeae which are gram negative, oxidase negative, rods
53
Why use API 20E?
biochemical identification of an unknown organism
54
T/F
in preparing for the API 20E the organism suspension should have a clearly visible turbidity equal to the 0.5 McFarland turbidity standard.
TRUE
55
T/F with API 20E you should accept a result \>80%
false -- you should accept a result of \>90%
56
T/F the morphology and staining characteristics of the Enterics are similar, making it difficult to distinguish them
True
57
T/F
in the Enterics antimicrobial susceptibility is difficult to predict
true
58
What media grow Enteric species?
Blood
MacConkey
XLD
Hektoen
Brilliant Green
59
What is the purpose of antimicrobial susceptibility tests?
to determine if a course of treatment will work in vivo
60
How is antimicrobial susceptibility tested?
Kirby-Bauer, Minimal Inhibitory Concentration (MIC)
61
The E-test and the Broth microdilution are part of which type of antimicrobial susceptibility test?
MIC
62
Which organization wrote interpretation criteria for antimicrobial susceptibility tests?
Clinical and Laboratory Standards Institute (CLSI)
63
T/F a clinical outcome can easily be predicted from an antimicrobial susceptibility test:
false -- Predicting clinical outcome based on susceptibility testing is extremely difficult due to other factors (site of infection, pharmacodynamics, etc)
64
Which susceptibility method(s) create(s) a zone size?
Kirby- Bauer
65
What is the standard agar base used to carry out antimicrobial susceptibility testing?
Mueller Hinton plate
66
T/F antimicrobial susceptibility testing should only be performed on clinically significant bacteria
True
67
Which susceptibility method(s) create(s) an MIC?
E-test and Broth microdilution
68
What is the definition of an “intermediate” result in antimicrobial susceptibility testing?
may still be effective against the bacterium but less so than a susceptible isolate
69
During a Kirby-Bauer test, how many times should the plate be streaked?
3 times and then the plate should be rimmed
70
T/F you should carefully move a disk with a loop on the Kirby-Bauer test if the dispenser put it in the wrong location
false -- once the disk touches the agar, it should not be moved
71
How is an E-test measured?
read at the point where the clear area (ellipse) meets the strip
72
What is reported in an E-test?
the MIC and the interpretive criteria (sensitive, intermediate, resistant)
73
What is one of the most important components of PCR?
a pair of synthetic oligonucleotides to primer DNA synthesis
74
T/F before synthesizing a primer it is prudent to scan DNA databases to check that the proposed sequence occurs only in the desired gene and not in vectors or undesired genes
True
75
How long should a primer be?
18-35 nucleotides
76
T/F members of a primer pair should not be more than 8 base pairs longer than each other
false -- members of a primer pair should not be more than 5 base pairs
77
How much of a primer should constitute C+G?
40 - 60%
78
What is the danger of repeated and self complementary sequences longer than 3 base pairs in a primer?
tends to make hairpin structures and prevent
primer binding to the target
79
What is the danger of complementarity between primer pairs?
primer dimers will form and result in no or low product yield
80
What is the formula for melting temperature of primers?
Tm (in celcius) = 2(A+T) + 4(G+C)
81
How many degrees difference can the melting temperature between primer pairs be?
5 degrees
82
. T/F it is necessary to add restriction sites to primers
false -- this is dependent on what you are supposed to do with the PCR product
83
Which end of the primer do you add the restriction sites?
5'
84
Why are base pairs added to the end of the restriction sites?
To increase efficacy of cleavage
85
What does ELISA stand for?
Enzyme Linked ImmunoSorbent Assay
86
What is detected by ELISA?
antigens or antibodies of interest
87
What are the different forms of the ELISA?
direct, indirect, sandwich
88
T/F the basic concept of the ELISA is the qualitative and immunological detection of antigen or antibodies in a clinical sample
false -- the basic concept of the ELISA is the immunological detection and quantitation of antigen or antibodies in a clinical sample
89
What is direct ELISA?
used to detect an antigen after it has attached to the solid phase
90
What are the steps of direct ELISA?
Coating, blocking, detection, read results
91
What is an indirect ELISA?
primary antibody attaches to an antigen.
secondary antibody is attached to the primary antibody with a label, allowing for reading the sample
92
What is a sandwich ELISA?
a capturing antibody is absorbed into the solid phase
and it is
used to determine an unknown microbial infection
93
Why is it important in sandwich ELISA to use an antibody from a different animal species?
it prevents same-species antibody binding
94
Which types of ELISA require stringent optimization?
indirect
and
sandwich
95
What is the purpose of the decolorizer when Gram staining
Clear the color from selective bacteria
96
What is the purpose of the counterstain of the Gram stain?
To color GRAM NEGATIVE bacteria
97
Which of the following bacteria is not KOH positive?
Any gram (+) bacteria will be (-) for KOH
*Staphylococcus *spp.
98
What is the reagent used in the catalase test?
Hydrogen peroxide
99
T/F
The differences between Pseudomonas and E.coli are the smell of grapes and the fact that Pseudomonas was oxidase negative
FALSE
*Pseudomonas* is oxidase POSITIVE
100
What does the dispersion on the MOI medium mean?
Motility
101
What does TSI not selective for?
Motility
102
Which sugar is not a part of the TSI medium?
MALTOSE
(glucose, sucrose and lactose ARE)
103
Which of these does not include the specific antigen-antibody complex?
\*PCR
104
T/F
Fungi are stained by all of the following
Gram, Cotton, PAS
TRUE
105
Non selective media?
*Sabauraud's Dextrose Agar*
106
What AA is involved in indole?
tryptophan
107
Oil immersion lens magnifies how much?
100x
108
What bacteria is metallic green on Eosin-Methylene Blue agar?
*E. coli*
109
T/F
When finding the zone of inhibition, you measure the radius of lysis on the plate
FALSE
diameter
110
In an oxidase/fermentation test, the results were 2 yellow tubes.
What bacteria do you have?
Facultative anaerobe
111
How do you differentiate between Enterobacteria and Pseudomonas?
Oxidase test (Pseudomonas is Oxidase +)
112
How do you
Distinguish Streptococcus from Rhodococcus?
Catalase Test
Streptococcus is (-)
113
T/F
You should collect blood samples minutes apart
FALSE!
HOURS apart
114
T/F
Plates are incubated inverted
TRUE
115
When do you check a
Micro ID?
After 4 hours
116
What is the 3rd reagent in Gram staining?
Alcohol
117
T/F
PCR tests for antibodies
FALSE
DNA/RNA
118
T/F
Fungi can’t grow on MacConkey agar (it is selective)
TRUE
119
Mannitol salt agar is used to grow what bacteria?
*Staphylococcus*
and it is a selective medium for this
120
What is chlorahexidine?
A bench cleaner
121
Dog has abscess, you take a swab from the outside and plate it. Results showed growth of coagulase negative staphylococci. You take a sterile aspirate of the center of the abscess and plate it. Results show Staphylococcus aereus. What can you tell your client?
Organism on the outside is Non-pathogenic while
Staphylococcus aereus is Pathogenic
122
Dog comes into a clinic, you suspect UTI what diagnostic test do you first perform?
Plate on blood agar
123
T/F
Kirby Bauer is a low cost test
TRUE
124
What are the 3 Methods for antimicrobial susceptibility testing?
Kirby Bower Disc Diffusion, Microdilution Broth, E Test
125
Who uses Kovac’s Reagent?
Oxidase test and MIO
126
You perform TSI and your results show a yellow slant, negative for gas production and a black butt. You write the report and include the following for your findings:
Acid Slant, Acid Butt, positive H2S production
127
Real Time PCR process is Denaturation, Annealing and Extension. What temp for Denaturation?
92°C (in notes it’s 94°C but no choices are close to this other than 92 °C)
128
E.coli turns the medium Yellow with yellow colonies
in what medium?
XLD agar
129
XLD is Selective and Differential for Enteric Pathogens, Especially to distinguish
\_\_\_\_\_\_ from \_\_\_\_\_
*Salmonella *from *Shigella*
130
Crystal Violet and Bile Salts Inhibit Gram (+) and many Gram (-)
on what medium?
MacConkey agar
131
XLD agar and TSI , what is used by Salmonella to produce H2S (Hydrogen Sulfide)?
Sodium Thiosulfate
Salmonella (or other bacti) + Sodium Thiosulfate--\> H2S
H2S + Ferric Ammonium Citrate--\> Black Color
