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Micro Bio 325 > Midterm 3 > Flashcards

Midterm 3 Flashcards

(110 cards)

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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
Index Ex
Listeria genus, coagulase + staph, generic E. coli
26
Indicator organism
Organisms that reflect the general bacteriological quality or safety of a sample
27
Indicator ex
APC, coliforms, yeast, molds
28
Indicator characteristics
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
29
Coliforms
Gram - Non spore forming Rod Ferment lactose to acid and gas 5 genera of Enterobacteriaceae
30
Fecal coliforms + safety
Coliforms that produce acid and gas (higher tem) Primarily E. coli Identify non bacterial microbes (viruses)
31
Indicators of quality
Usually specific Yeast, mold, lactic acid bacteria APC not as specific
32
Microbial sampling
Identify production lots within a level of confidence that are inferior or unsafe
33
Production lot
Quantity of food produced, handled, and stored within a limited time period under uniform conditions
34
Risk assessment considerations
Target population Transportation and storage Preparations What microbes are found in what foods
35
Incidence
of positives per x samples 6% per 100 samples (ex) Presence or absence
36
Level
Enumerate organisms # of cells per x samples
37
Representative sample
Similar as possible to that of the lot from which it was drawn from Random Consistent and represent the entire lot
38
2n sampling plan
n = # of samples m = max level of microbe c = max # of samples with UNACCEPTABLE results + or - (yes or no)
39
3n sample plan
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
40
Agglugination Pros
Simple, no special equipment, fast
41
Agglugination Cons
Sometimes difficult to interpret, nonspecific reactions
42
Immunoprecipitation Pros
Simple, no extra equipment
43
Immunoprecipitation Cons
Not quantitative, subjective
44
Immunoconcentration Pros
Very rapid, enhanced specificity, adapt to almost any existing rapid method
45
Immunoconcentration Cons
Added cost
46
ELISA Pros
Sensitive, not radioactive, can be quantitative
47
ELISA Cons
Hands on time + equipment needed
48
Rapid methods
Mini biochemical kits Antibody based Nucleic acid based
49
Biochemical kits
Use chromogenic or flourescent substrates X Gal MUG
50
Immuno Assays
Agglugination Immunoprecipitation Immunoconentration ELISA
51
Modeling
Use mathematical tools to predict behavior of 1+ type of microbe Useful for assessing risk, predicting efficacy of treatments
52
Subtyping
Characterization below the species or subspecies level
53
Significance of subtyping
Recognition of outbreaks Identification of source Characterization of clones
54
Discriminatory power
The ability of a method to discriminate, segregate, or discern differences between two isolates of the same species
55
Fermentation def
Catabolism of carbon sources where organic compounds serve as the ultimate e- acceptor to produce ATP in the absence of O2
56
Phosphorylation
Movement of e- generated from light interaction with pigment via membrane bound transport system creates NRG for ATP synthesis
57
Oxidative phosphorylation
Movement of e- generated from metabolism through membrane bound transport system creates NRG for ATP synthesis
58
Substrate level phosphorylation
Phosphate is transferred from high NRG carbon intermediate generated during catabolism Occurs during fermentation
59
Glycolysis steps
Activation of glucose Splitting of hexose Energy derivation
60
Glycolysis outputs/inputs
1 Glucose - 2 ATP + 4 ATP (2 Net) + 2 NADH
61
Purpose of fermentation
Free up NAD+ so glycolysis can continue
62
End products: Streptococcus, lactobacillus, bacillus
Lactic acid
63
End products: Yeast
Ethanol CO2
64
Benefits of microbes
Preserve foods Competitive exclusion Vitamin production Flavor Improve safety Improve starch digestability Lower toxin level
65
Fermenatation products
Antibiotics Hormones Enzymes Ethanol CO2 H2 Acids Amino Acids Vitamins Gums
66
Fermenters: Bacteria
Lactobacillus Lactococcus Streptococcus Leuconostoc Propionibacterium
67
Fresh Pack
Take vinegar + add spice + veg Not fermented
68
Pickle fermentation
Cucumber placed in salted water (brine) Carbs released Normal flora on the surface ferment carbs
69
Pickles initial microbes
Leuconostoc mesenteriodes Enterococcus faecalis
70
Pickles primary microbes
Lactobacillus plantarum + brevis
71
Pickles results
Homolactic (only lactic acid) No CO2 produced pH drops coliforms/enterics If yeast grow → bubbles + CO2
72
Sauerkraut fermentation
Shred cabbage Add and distribute salt Place in tank with no brine Cover with plastic Water to keep anaerobic
73
LAB
lactobacillus Streptococcus Leuconostoc
74
Yogurt Starter Culture
Streptococcus thermophilus Lactobacillus delbrueckii ssp. bulgaricus
75
Blue, Roquefort, Gorgonzola cheese microbes
Penicillium roqueforti Penicillium glaucum
76
Cheese milk contaminant
Psuedomonas Heat stable lipases
77
Cheese Steps
Milk Prep Heat Treatment Add starter culture Add rennet Cut Separate curds from whey Salt, press, ripen
78
Intrinsic and extrinsic factors of cheese
Different pH (based on cheese) Salt Temp control Competition
79
Cheese and MC
Rate of acid production affects MC
80
Meat Starter Culture
Drops pH Need to add glucose Break down protein, lipids, carbs Tiem and temp dependent Control final pH with glucose
81
Meat Steps
Mixing Final Grind Stuff Thermal Processing Drying
82
Meat Main Pathogen
Staph aureus
83
Probiotics
Live microbes that provide health benefits when consumed
84
Prebiotics
Select for replication of beneficial microbes Non digestible oligosaccharides
85
Strata
Division of population into smaller groups
86
APC hazard
Utility
87
E. coli hazard
Indicator
88
Salmonella hazard
Severe
89
Staph hazard
Moderate
90
LM hazard
Severe
91
Utility microbes
Yeast, mold, total count
92
Indicator microbes
Coliforms, E.coli, fecal E. coli
93
EHEC hazard
severe
94
Why is spoilage not necessarily a bad thing
Competition for pathogens Quality decrease, people won't consume the food and won't get sick
95
Key point
Lower specifications for incoming ingredients to achieve shelf life
96
Why retesting is bad
The probability of getting 2 x positives is very low
97
subtyping methods
Pulse field Sequencing
98
Why we subtype
Match product isolate to patient isolate Helps with sources for outbreaks Match source of spoilage microbes
99
Most specific methods
Nucleic acid based
100
Modeling
If equipment breaks Plug info into program Quick
101
Modeling cons
Data not generated from real food Some inaccuracies
102
Modeling pros
Quick Good tool for ballpark
103
Feeding grass vs corn and E coli
Feed corn to cattle lowers intestinal pH Grass-fed shed lower #s of E. coli per gram (greater amount of feces) (wash)
104
Feeding corn caused evolution of EHEC
Action doesn’t cause something to evolve Trait got selected for Horizontal gene transfer = more rapid than mutations
105
Farmer processing in open air
Lower CFU/g than commercial birds Not very significant difference
106
Who is responsible for keeping food safe
Gov? Everyone? Producers?
107
Who is responsible for Kevin's death
Jack in the box Beef producer Cook Feed lot owner Manufacturing plant Lobbyist
108
Ensure another death doesn't happen
Limit the # of places you get the meat from Tight specifications Animal husbandry Buy local meat Manage runoff of manure
109
Make healthy food available to everyone
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
Live vs dead solution
Test at diff times Test for RNA

Micro Bio 325 (5 decks)

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