Lab Flashcards

1
Q

what antiseptics/disinfectants disrupt the lipid bilayer

A

alcohols, soaps, detergents

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2
Q

what antiseptics/disinfectants are oxidizing agent

A

hydrogen peroxide, halogens, metals, aldehydes, ethylene oxide, benzalkonium chloride

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3
Q

what antiseptics/disinfectants break H bonds

A

acids and bases

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4
Q

what is the function of pasteurization

A

heat to reduce number of microbes but not to zero

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5
Q

besides time, what is the main difference between vat, high temperature, and ultra pasteurization

A

temperature

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6
Q

what are the temperature differences between vat, high temperature, and ultra pasteurization

A

vat= 145F (63C)
high temp= 161F (72C)
ultra= 280F (138C)

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7
Q

how does an autoclave work

A

it holds water at 121C and 2x atmospheric pressure for 15 minutes to destroy all microbes including spores

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8
Q

what type of setting is UV radiation used in for sterilization

A

hospital

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9
Q

how does ionizing/gamma radiation work

A

creates free radicals to damage DNA

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10
Q

what is gamma radiation used for

A

to sterilize items that can’t be put through an autoclave (ex: plastics)

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11
Q

what is involved in liquid filtration

A

sterilized liquids by passing them through a filter with 2 micrometers

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12
Q

when is liquid filtration used

A

when heating would kill something you wanted to preserve

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13
Q

how does a hemocytometer/Petroff-Hausser Counter with microscopy work to count bacteria

A

it uses a microscope slide with grids
the volume of each square is known so you can count the number of cells in each square and multiple to determine the number of bacteria in the liquid sample

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14
Q

how does spectrophotometry work

A

a line is shined though the liquid sample and the amount of light blocked is used to determine the number of bacteria in the sample by comparing it to McFarlands 0.5 standard

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15
Q

what are 2 limitations with spectrophotometry

A

production of biofilm increases bacteria size so you may be over-counting
can’t be used with samples that are too dark or too opaque

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16
Q

what is the concentration and number of bacteria in McFarlands standard

A

0.5
1x10^8 bacteria/mL

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17
Q

how many bacterial colonies must be present on a plate to count

A

30-300

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18
Q

what are 2 limitations to counting bacteria on a plate

A

biofilm causes bacteria to stick together so each colony may represent more than 1 bacteria
having more than 300 colonies is likely that some colonies represent more than 1 bacteria leading to undercounting

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19
Q

what is the dilution standard for antibody/antigen samples

A

1:2

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20
Q

in titers, the __ the second number, the more antibody present (higher or lower)
ex: is 1:16 or 1:64 a greater titer

A

higher
1:64

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21
Q

what causes zeta potential in RBC

A

sialic acid on the RBC surface creates a net - charge that IgG is too small to overcome, therefore IgM must be used for crosslinking

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22
Q

what antibody does blood typing use

A

anti-RBC IgM

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23
Q

what is the question asked for the indirect Coomb’s test

A

is there IgG that binds to the RBC
*used maternal serum

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24
Q

what is the question asked for the direct Coomb’s test

A

does the RBC have IgG stuck to it
*uses fetal RBC

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25
Q

how does radial immunodiffusion differ from double immunodiffusion

A

radial determines the amount of antigen in the sample
double immunodiffusion tells us if the antigen is present or not

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26
Q

do immunoassays use monoclonal or polyclonal antibodies

A

mono

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27
Q

what is ELISA used for

A

to detect protein/antigen in serum using antibodies
*can be used to determine titer

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28
Q

what does ELISPOT TSpot test for

A

how many cells dump out the protein of interest
*more spots on plate= more cells that released the protein/cytokine

ex: if T cells make IFN gamma
“is IFN gamma released in response to tuberculosis antigen?”

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29
Q

what is the function of immunohistochemistry

A

used to access tissue location a protein localizes in

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30
Q

what results does fluorescence activated cell sorting (FACS) give is

A

percent of cells that express a specific marker and level of expression
(flow cytometry)

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31
Q

what does neutrophil functional assay tell us

A

if oxidative burst is functioning and NADPH oxidase is made (shift in flow cytometry= working)

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32
Q

what is the function of leukocyte function assay

A

determine if B and T cells have normal activity by using something you know will activate all B or all T cells

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33
Q

what 2 things can be used to stimulate T cells in leukocyte function assay

A

PHA
antibodies against CD3 and CD28

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34
Q

what is used to stimulate B cells in leukocyte function assay

A

antibody against antibody
(ex: antibody against IgG)

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35
Q

how do you measure T cell proliferation

A

used fluorescence based assay, dye the cytoplasm, stimulate T cells, notice degree of decreasing fluorescence

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36
Q

how would you perform a functional assay for apoptosis

A

isolate monocytes/T/B cells
treat with PHA to stimulate T cells
culture with IL-2 for T cell proliferation
add anti-FAS antibody to trigger apoptosis
use TUNEL assay to detect fragmented DNA

*undergoing apoptosis= cell will fluoresce

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37
Q

how can you test for T cell maturation

A

if cells are actively undergoing VDJ recombination in the thymus, the T cell receptor excision circles will be detected in the blood

if they are absent, there is no VDJ recombination= no T cells= can be used to detect SCIDs

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38
Q

what is the function of CH50 test (complement hemolysis 50%)

A

test if complement is working or if it has been used up

less complement= CH50 closed to 1:2

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39
Q

what is the Cr51 release assay used to test for

A

CD8+ T cell function

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40
Q

when should modified acid-fast staining be performed

A

for actinomyces, fungi, and some parasites

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41
Q

if everything turns pink, what happened with the gram stain

A

too much decolorizer

42
Q

if everything is purple, what happened with the gram stain

A

not enough decolorizer

43
Q

what bacteria does MacConkey agar select against

A

gram + and bacteria that can’t grow in the presence of bile

44
Q

what does it mean if MacConkey agar turned pink

A

bacteria ferments lactose

45
Q

what does eosin methylene blue agar select against

A

gram +

46
Q

what does if mean if the eosin methylene blue agar turned dark green/black

A

the bacteria ferments lactose

47
Q

what does mannitol salt agar select against

A

bacteria that need high water activity to grow

48
Q

what does it mean if mannitol salt agar turns yellow

A

the bacteria ferments mannitol

49
Q

what bacteria show on ESBL agar

A

e.coli O157.H7 is pink
MRSA is blue
all other bacteria are white

50
Q

TSI slants are used as a differential for what 3 characteristics

A

acid production (fermentation)
gas production
precipitation of metal

51
Q

what 2 media allow for precipitation of a metal

A

Hektoen enteric agar
tellurite containing blood/chocolate agar

52
Q

what is charcoal buffered yeast agar used for

A

charcoal absorbs toxic metabolites generated by growing bacteria

53
Q

what is chocolate agar used for

A

to grow bacteria that need components or RBC to grow but don’t have the enzymes to break down RBC on their own

54
Q

what is the function of PCR

A

look for presence or absence of 1 specific gene
(ex: antibiotic resistance or virulence factor gene)

55
Q

what is the function of rt-PCR

A

determine viral load of a virus with an RNA genome

56
Q

what is the function of western blot
what infection is it often used for

A

looks for the amount of one protein made
HIV

57
Q

what is pulse field gel electrophoresis (PFGE) used for

A

determine whether the organism is of the same strain
(used to identify foodborne illness outbreaks)

58
Q

what is multi-locus sequence typing used for

A

to measure evolutionary relatedness by identifying point mutations
*more detailed than PFGE

59
Q

what is ribosomal RNA sequencing used for

A

identify organisms at the species level

60
Q

what are the steps to determine if molecular Kochs postulates have been met

A

mutate isolate to knockout the gene
perform artificial transformation to reintroduce a plasmid containing the gene
if reintroduction of the gene into the bacteria leads to the bacteria causing symptoms again, the pathogenic gene has been identified and postulates have been satisfied

61
Q

how much blood should be collected for culture in adults vs children vs neonates

A

adults: at least 20mL
children: at least 10mL
neonates: 2mL

62
Q

how can culturing be used to determine if meningitis is caused by bacterial or fungal infection

A

compare the glucose concentration in the blood vs in CSF
Viral= normal glucose
Bacterial or fungal= low glucose

63
Q

once blood is collected, how is it distributed in vials

A

half in a viral for anerobic organisms
half in a vial for aerobic organisms

64
Q

when is a broncho-alveolar lavage used

A

if a sample needs to be taken but no sputum is being produced for collection

65
Q

how does ViTEK identify organisms

A

based on culture characteristis

66
Q

how does MALDI-ToF identify organisms

A

based on molecular signatures of different bacteria/fungi/parasites

67
Q

how does BioFire identify an organism

A

by testing for the presence or absence of multiple genes simultaneously

68
Q

why is MALDI-ToF not often used in hospital

A

it is expensive for the machine and subscription to databases

69
Q

what is the main advantages of MALDI-ToF to identify an organism

A

results within 2 hrs= faster diagnosis

70
Q

what are the 2 main advantages of BioFire to identify an organism

A

organisms don’t have to be grown (uses the direct sample)
primers cover the most common pathogens with the symptoms present

71
Q

what agar is used for the Kirby Bauer test

A

Mueller Hinton

72
Q

how does minimum inhibitory concentration differ from minimum bacterial concentration

A

MIC- lowest concentration to prevent bacterial growth
MBC- lowest concentration to kill bacteria

73
Q

what is the difference between primary cell culture vs diploid cell strain vs continuous cell line

A

primary- cells taken from a living animal, keep alive as long as possible
diploid- cells of single cell type can be cultured approx. 50 times
continuous- malignant cells can be cultured an infinite number of times

74
Q

what is the cytopathic effect with viruses

A

even if we can’t see visible virus, we know there was infections based on changes in the cell that the virus made

75
Q

if a virus is a DNA viral, inclusion bodies will be found in __. If RNA, they will be found in __

A

DNA- nucleus
RNA- cytoplasm

76
Q

what is used to determine the number of viruses in a sample

A

viral plaque assay

more virus= more cells killed= more plaques

77
Q

for viruses, samples need to be collected within __ days of symptoms

A

3-7

78
Q

viral samples for nucleic acid detection must be kept at __C or frozen at __

A

4C
-70C

79
Q

for detection of various viral strains, what are primers used to detect

A

hemagglutinin and neuramidase (each are strain specific)

80
Q

for use of ELISA to detect viral proteins, how is it performed

A

add specific antibodies to blood
antigen will bind to antibody
add a secondary antibody to visualized bound antigens

81
Q

what question is hemagglutination answering

A

how much virus is there

82
Q

how is hemagglutination interpreted

A

the more virus, the more hemagglutinin, the more clumping (seen fuzzy in well plate)

83
Q

what question is hemagglutinin inhibition answering

A

is there antibody that binds to the virus

84
Q

how is hemagglutination inhibition results interpreted

A

higher hemagglutinin inhibition= more antibody= less clumping (seen as a button on well plate)

85
Q

what method of identification would not be used to identify a virus

A

electron microscopy

86
Q

how do cassette based tests work

A

viral proteins are bound to a nitrocellulose membrane
antibodies bind to these proteins
the control line is loaded with IgG so it will always show since the sample will always have IgG
the test line has the peptide of interest so the patient’s antibodies will stick to the antigen
protein A colloid gold conjugated binds to the Fc portion of the antibody allowing for a visible colored time for test results

87
Q

ELISA and flow cytometry (FACS) both measure protein expression. how do they differ in their measurement

A

ELISA- protein in serum/culture
flow cytometry (FACS)- protein expression on cells

88
Q

is fluoride always toxic

A

no, it depends on the concentration

89
Q

what would we use to filter bacteria from solution containing it’s toxin

A

liquid filtration

90
Q

what size of filtration will not allow bacteria to pass

A

0.2micrometers

91
Q

what would we use to check a bacteria sample in saline that is MRSA after inoculation on a plate

A

McFarland

92
Q

what agar would be used to isolate intestinal bacteria that are gram -

A

MacConkey

93
Q

what does the color change on eosin methylene blue agar indicate about the bacteria

A

lactose fermenting

94
Q

what culture method should be used to see if something from a pond can grow on skin

A

Mannitol salt agar

95
Q

what culture method would you use to test if an organism can live on human skin

A

mannitol salt agar

96
Q

if a bacteria that is beta hemolytic when near bacteria that lyse RBC is grown on its own, what type of agar is needed

A

chocolate

97
Q

what test would you use to compare 2 types of pathogens based on 1 gene

A

PCR

98
Q

if an adult is suspected of having bacteremia, how would you diagnose it

A

draw 20mL blood and divide half and half into an anaerobic tube and an aerobic tube

99
Q

why would a urine sample contain erythrocytes and gram positive and negative bacteria, but no leukocytes

A

contamination by normal vaginal flora and menstrual blood

100
Q

why would we use a monoclonal antibody

A

it has high specificity

101
Q

what benefits does immunohistochemistry provide

A

it allows us to visualize specific locations of cells and tissues that were targeted

102
Q

what would be the secondary reagent in an indirect fluorescent antibody test

A

fluorochrome bound to an anti-human Ig