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Micro Bio 325 > Midterm 3 > Flashcards

Midterm 3 Flashcards

1
Q

Challenges of testing

A

Bacteria not uniformly distributed

Food matrices interfere

Indigenous microbes (not sterile)

Pathogen of interest is in lower #s

Injury to pathogen (give time to recover before selective tests)

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2
Q

MPN

A

Dilution of food samples
9 or 15 tubes
3 or 5 replicates of each

Based on stats
Dilute to extinction
Higher estimate than colony counts

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3
Q

MPN scores for

A

Positivity
Total bacteria
Lactose fermenting
LST MUG

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4
Q

Why does broth have higher counts than plates

A

Easier to grow in broth than on a plate

More ideal to grow in liquid

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5
Q

LST MUG

A

Select for enteric

MUG cleaved by GUD ⇒ MU (add light = fluorescence)

Yields E coli count

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6
Q

Immunoassays

A

Antibody specific to antigen
Need specific antigen to organisms of interest
Inject in animal → make antibodies → use for detection

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7
Q

Agglutination

A

Lattice of antibodies and antigens

Mix colony w/ antibodies → clumping

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8
Q

Immunoprecipitation

A

Control and test lanes

Antibodies in the sample well

Complex and wick up the wick

Capture antibody captures if antigen is present

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9
Q

Immunoconcentration

A

Enriched sample

Add to test tube

Add metal beads w/ antibody attached

Mix + incubate

Use magnet to collect beads

Wash off unbound

Streak out (differential and selective)

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10
Q

ELISA

A

Enzyme conjugated to antibody or antigen
Wash, then react with the substrate
Shows a visible color change

enzyme-linked immunosorbent assay
have to do enrichment 1st
Need antibody specific to microbe

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11
Q

Sandwich Method

A

Enrichment 1st

Solid matrix (solid is charged) attached to antibodies

Put the enriched sample in well

Antibody look for antigens + capture it

Wash everything not bound

Add 2nd antibody with enzyme tag (same target, diff epitope)

2nd antibody attaches

Wash again

Add substrate

Colorimetric end product

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12
Q

Nucleic acid based
Pros/Cons

A

Sensitive, specific, fast

Need specific gene
Matrix interference
cost
Live vs dead

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13
Q

PCR

A

Denature with heat

Need specific primer (brackets target gene)

Anneal the primer to the strand

Add polymerase + replicate

Need Taq polymerase

Takes a few hours

Run a gel electrophoresis to analyze

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14
Q

TaqMan PCR

A

Removes running of gel with fluorescent tag

2 primers + 3rd probe bracketed by primers

Positive or negative result (fluorescence or not)

If tag is adjacent to the quenching agent → no fluorescence

Polymerase chews probe and releases components –> components spread out → fluorescence

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15
Q

PFGE

A

Pulsed field gel

Changes orientation to a zig zag pattern
Separate large lengths of DNA (long, tedious)

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16
Q

Contributions to variation

A

Insertion
Deletion
Recombination
Phage
Plasmid

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17
Q

Most discriminatory subtyping method

A

Sequencing

Ultimate method to identify differences btwn 2 isolates

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18
Q

Method consideration

A

Approval status
time
Cost
# of samples
Equipment

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19
Q

Microbiological criteria

A

Asses the
- Safety
- Quality
- Adherence to GMPs
- Suitability

of a food/ingredient for a particular purpose or target population

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20
Q

Standard

A

Microbiological criteria that is part of law, ordinance, or regulation

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21
Q

Guideline

A

A microbiological criterion used by the food industry and regulatory agency to monitor a manufacturing process

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22
Q

Specification

A

Microbiological criterion that is used as a purchase requirement between a buyer and vendor

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23
Q

Criteria: include

A

Identify of food
Identity of contaminant of concern
Method for detection
Sampling plan
Microbiological limits

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24
Q

Index organism

A

Organism that signals the possible presence of pathogenic or toxigenic organisms within a sample

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25
Q

Index Ex

A

Listeria genus, coagulase + staph, generic E. coli

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26
Q

Indicator organism

A

Organisms that reflect the general bacteriological quality or safety of a sample

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27
Q

Indicator ex

A

APC, coliforms, yeast, molds

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28
Q

Indicator characteristics

A

Easily and rapidly detectable

Easily distinguishable from other food flora

Consistent association with
pathogen whose presence it is to indicate

Growth/survival curve = that of pathogen

Present when pathogen is present

Absent in food free of pathogen

Possible specificity to intestinal tract

May occur in high # in feces

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29
Q

Coliforms

A

Gram -
Non spore forming
Rod
Ferment lactose to acid and gas
5 genera of Enterobacteriaceae

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30
Q

Fecal coliforms + safety

A

Coliforms that produce acid and gas (higher tem)
Primarily E. coli
Identify non bacterial microbes (viruses)

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31
Q

Indicators of quality

A

Usually specific
Yeast, mold, lactic acid bacteria
APC not as specific

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32
Q

Microbial sampling

A

Identify production lots within a level of confidence that are inferior or unsafe

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33
Q

Production lot

A

Quantity of food produced, handled, and stored within a limited time period under uniform conditions

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34
Q

Risk assessment considerations

A

Target population
Transportation and storage
Preparations
What microbes are found in what foods

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35
Q

Incidence

A

of positives per x samples
6% per 100 samples (ex)
Presence or absence

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36
Q

Level

A

Enumerate organisms
# of cells per x samples

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37
Q

Representative sample

A

Similar as possible to that of the lot from which it was drawn from
Random
Consistent and represent the entire lot

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38
Q

2n sampling plan

A

n = # of samples
m = max level of microbe
c = max # of samples with UNACCEPTABLE results
+ or - (yes or no)

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39
Q

3n sample plan

A

n = # of samples

c = max # of samples allowed with marginal results between m and M

Accept all below m

Accept c amount between m and M

Reject all above M

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40
Q

Agglugination Pros

A

Simple, no special equipment, fast

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41
Q

Agglugination Cons

A

Sometimes difficult to interpret, nonspecific reactions

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42
Q

Immunoprecipitation Pros

A

Simple, no extra equipment

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43
Q

Immunoprecipitation Cons

A

Not quantitative, subjective

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44
Q

Immunoconcentration Pros

A

Very rapid, enhanced specificity, adapt to almost any existing rapid method

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45
Q

Immunoconcentration Cons

A

Added cost

46
Q

ELISA Pros

A

Sensitive, not radioactive, can be quantitative

47
Q

ELISA Cons

A

Hands on time + equipment needed

48
Q

Rapid methods

A

Mini biochemical kits
Antibody based
Nucleic acid based

49
Q

Biochemical kits

A

Use chromogenic or flourescent substrates

X Gal
MUG

50
Q

Immuno Assays

A

Agglugination
Immunoprecipitation
Immunoconentration
ELISA

51
Q

Modeling

A

Use mathematical tools to predict behavior of 1+ type of microbe

Useful for assessing risk, predicting efficacy of treatments

52
Q

Subtyping

A

Characterization below the species or subspecies level

53
Q

Significance of subtyping

A

Recognition of outbreaks
Identification of source
Characterization of clones

54
Q

Discriminatory power

A

The ability of a method to discriminate, segregate,
or discern differences between two isolates of the
same species

55
Q

Fermentation def

A

Catabolism of carbon sources where organic compounds serve as the ultimate e- acceptor to produce ATP in the absence of O2

56
Q

Phosphorylation

A

Movement of e- generated from light interaction with pigment via membrane bound transport system creates NRG for ATP synthesis

57
Q

Oxidative phosphorylation

A

Movement of e- generated from metabolism through membrane bound transport system creates NRG for ATP synthesis

58
Q

Substrate level phosphorylation

A

Phosphate is transferred from high NRG carbon intermediate generated during catabolism

Occurs during fermentation

59
Q

Glycolysis steps

A

Activation of glucose
Splitting of hexose
Energy derivation

60
Q

Glycolysis outputs/inputs

A

1 Glucose

  • 2 ATP
    + 4 ATP (2 Net)
    + 2 NADH
61
Q

Purpose of fermentation

A

Free up NAD+ so glycolysis can continue

62
Q

End products:

Streptococcus, lactobacillus, bacillus

A

Lactic acid

63
Q

End products: Yeast

A

Ethanol
CO2

64
Q

Benefits of microbes

A

Preserve foods
Competitive exclusion
Vitamin production
Flavor
Improve safety
Improve starch digestability
Lower toxin level

65
Q

Fermenatation products

A

Antibiotics
Hormones
Enzymes
Ethanol
CO2
H2
Acids
Amino Acids
Vitamins
Gums

66
Q

Fermenters: Bacteria

A

Lactobacillus
Lactococcus
Streptococcus
Leuconostoc
Propionibacterium

67
Q

Fresh Pack

A

Take vinegar + add spice + veg
Not fermented

68
Q

Pickle fermentation

A

Cucumber placed in salted water (brine)
Carbs released
Normal flora on the surface ferment carbs

69
Q

Pickles initial microbes

A

Leuconostoc mesenteriodes

Enterococcus faecalis

70
Q

Pickles primary microbes

A

Lactobacillus plantarum + brevis

71
Q

Pickles results

A

Homolactic (only lactic acid)
No CO2 produced
pH drops coliforms/enterics
If yeast grow → bubbles + CO2

72
Q

Sauerkraut fermentation

A

Shred cabbage
Add and distribute salt
Place in tank with no brine
Cover with plastic
Water to keep anaerobic

73
Q

LAB

A

lactobacillus
Streptococcus
Leuconostoc

74
Q

Yogurt Starter Culture

A

Streptococcus thermophilus

Lactobacillus delbrueckii ssp. bulgaricus

75
Q

Blue, Roquefort, Gorgonzola cheese microbes

A

Penicillium roqueforti
Penicillium glaucum

76
Q

Cheese milk contaminant

A

Psuedomonas
Heat stable lipases

77
Q

Cheese Steps

A

Milk Prep
Heat Treatment
Add starter culture
Add rennet
Cut
Separate curds from whey
Salt, press, ripen

78
Q

Intrinsic and extrinsic factors of cheese

A

Different pH (based on cheese)
Salt
Temp control
Competition

79
Q

Cheese and MC

A

Rate of acid production affects MC

80
Q

Meat Starter Culture

A

Drops pH
Need to add glucose
Break down protein, lipids, carbs
Tiem and temp dependent
Control final pH with glucose

81
Q

Meat Steps

A

Mixing
Final Grind
Stuff
Thermal Processing
Drying

82
Q

Meat Main Pathogen

A

Staph aureus

83
Q

Probiotics

A

Live microbes that provide health benefits when consumed

84
Q

Prebiotics

A

Select for replication of beneficial microbes

Non digestible oligosaccharides

85
Q

Strata

A

Division of population into smaller groups

86
Q

APC hazard

A

Utility

87
Q

E. coli hazard

A

Indicator

88
Q

Salmonella hazard

A

Severe

89
Q

Staph hazard

A

Moderate

90
Q

LM hazard

A

Severe

91
Q

Utility microbes

A

Yeast, mold, total count

92
Q

Indicator microbes

A

Coliforms, E.coli, fecal E. coli

93
Q

EHEC hazard

A

severe

94
Q

Why is spoilage not necessarily a bad thing

A

Competition for pathogens
Quality decrease, people won’t consume the food and won’t get sick

95
Q

Key point

A

Lower specifications for incoming ingredients to achieve shelf life

96
Q

Why retesting is bad

A

The probability of getting 2 x positives is very low

97
Q

subtyping methods

A

Pulse field
Sequencing

98
Q

Why we subtype

A

Match product isolate to patient isolate
Helps with sources for outbreaks

Match source of spoilage microbes

99
Q

Most specific methods

A

Nucleic acid based

100
Q

Modeling

A

If equipment breaks

Plug info into program

Quick

101
Q

Modeling cons

A

Data not generated from real food

Some inaccuracies

102
Q

Modeling pros

A

Quick

Good tool for ballpark

103
Q

Feeding grass vs corn
and E coli

A

Feed corn to cattle lowers intestinal pH

Grass-fed shed lower #s of E. coli per gram (greater amount of feces) (wash)

104
Q

Feeding corn caused evolution of EHEC

A

Action doesn’t cause something to evolve

Trait got selected for

Horizontal gene transfer = more rapid than mutations

105
Q

Farmer processing in open air

A

Lower CFU/g than commercial birds
Not very significant difference

106
Q

Who is responsible for keeping food safe

A

Gov? Everyone? Producers?

107
Q

Who is responsible for Kevin’s death

A

Jack in the box
Beef producer
Cook
Feed lot owner
Manufacturing plant
Lobbyist

108
Q

Ensure another death doesn’t happen

A

Limit the # of places you get the meat from
Tight specifications
Animal husbandry
Buy local meat
Manage runoff of manure

109
Q

Make healthy food available to everyone

A

Consumer education

Government has to be part of solution

Subsitdes or food vouchers to level out playing field

Subsidize small companies instead of large ones

Food trucks in food deserts

110
Q

Live vs dead solution

A

Test at diff times
Test for RNA

Micro Bio 325 (5 decks)

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