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Food-Borne Pathogens > Introduction > Flashcards

Introduction Flashcards

1
Q

Intrinsic factors

A

Factors inherent to the food (ph, water activity, nutrients)

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2
Q

Extrinsic factors

A

Factors external to the food (temp, gas, atmosphere)

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3
Q

Autotrophic

A

Carbon from CO2 through carbon fixation

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4
Q

Heterotrophic

A

Carbon from organic coompounds

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5
Q

Chemotrophic

A

Energy from chemical

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6
Q

Phototrophic

A

Energy from light

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7
Q

Lithotrophic

A

Reducing equivalents come from inorganic compounds

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8
Q

Organotrophic

A

Reducing equivalents come from organic compounds

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9
Q

Anaerobic terminal electrons acceptors are not found where

A

In food bacteria

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10
Q

Thermophilic

A

Grow at 50C or above

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11
Q

Thermoduric

A

Survive pasteurization

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12
Q

Psychrotrophic

A

Grow in fridge

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13
Q

Cryophilic

A

Grow in freezer

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14
Q

Halophilic

A

Grow in salt

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15
Q

Aciduric

A

Survive at low pH

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16
Q

Turgor pressure

A

Exists because bacteria live in environments more dilute than cytoplasm, causes a net influx of water

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17
Q

Gram positive

A

Thick peptidoglycan

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18
Q

Gram negative

A

Thin peptidoglycan, outer membrane

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19
Q

Teichoic acids

A

On gram positive

30-60% of cell weight, anchored to peptidoglycan

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20
Q

Lipopolysaccharide

A

On gram negative

Lipid A core, repeating oligosaccharide (O antigen)

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21
Q

Sex pili

A

Used for bacteria to attach to each other and transmit DNA from cell to cell
Found in enteric bacteria but not universal among bacteria

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22
Q

K antigen

A

Capsule

Repeats HMW structures to form capsule

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23
Q

O antigen

A

Lipopolysaccharide
Consist of lipid and polysaccharide; joined by covalent bond
In gram negative

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24
Q

F antigen

A

Fimbriae
Both gram neg and pos
Rarely used in classification

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25
Q

H antigen

A

Flagella

Based on reaction with the flagellin protein

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26
Q

5 physiological/physical states of bacteria

A

Vegetative, injured, VBNC, biofilms, sporulated

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27
Q

Injured cell

A

Can grow on non-selective media but not selective media

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28
Q

What can adding a peroxide detox to injured cells do

A

Help them over come damage caused by oxygen toxicity

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29
Q

VBNC

A

Cannot be cultured on any media even though viability can be demonstrated by non-culturable methods

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30
Q

How can VBNC viability be demonstrated

A

Cytological methods

Substrate responsive metabolism

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31
Q

VBNC is most often induced by…

A

A nutrient limitation

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32
Q

Signal transduction

A

Protein spans membrane, molecule binds protein and elicits response

33
Q

Quorum sensing

A

Autoinducers diffuse through membrane to elicit response

34
Q

What does auto induced mean

A

Signal compound is made by a gene product of the same regulon of the thing that is affected (transcribed)

35
Q

Two component signal transduction consists of…

A

Histidine kinase and response regulator

36
Q

Pleiotrophic

A

Occurs when one gene influence two or more seemingly unrelated phenotypic traits

37
Q

Endospores

A

Differentiated cells that are very resistant to heat and cannot be easily destroyed

38
Q

What does it mean that bacterial chromosomes are plastic

A

The combinations of genes present will be different in every isolate (some missing, some unique)

39
Q

Core genome

A

Genes shared by all members of a certain group

40
Q

Pangenome

A

Genes are present in any member of a certain group

41
Q

Accessory genome

A

Genes that are present in a subset of members of a certain group

42
Q

Prophage

A

Bacteriophage genome inserted into the circular bacterial DNA chromosome

43
Q

Lysogenic conversion

A

The process by which a prophage converts a nonpathogenic bacteria to a pathogen

44
Q

Defective prophage

A

Can no longer form infective phage because of loss of essential genes

45
Q

Why can DNA elements be suspected of being defective prophages

A
  1. not common in all strains of a species

2. carry genes related to other pathogens

46
Q

Plasmids

A

Circular molecules of dsDNA that are self replicating (in some cases linear)

47
Q

What do plasmids carry

A

Genes which encode for products which can benefit the bacteria under certain circumstances

48
Q

Insertion sequence elements

A

Smallest transposons, only encode the transposon, can interrupt gene function
Usually have inverted repeat on either end

49
Q

Composite transposons

A

When two IS elements bracket other genes and and take them with them when they move

50
Q

Vertical gene transfer

A

Transmission of DNA from mother to daughter cells

51
Q

HGT

A

Movement of DNA from one bacteria to another

52
Q

Three divisions of foodborne illness

A

Intoxication, infection and toxicoinfection

53
Q

Intoxication

A

Ingestion of toxin that grew in the food

Must be present in its active form

54
Q

Infection

A

Illness after eating viable cells

Multiply in digestive tract

55
Q

Toxicoinfections

A

Illness after eating a large number of cells that sporulate, colonize, or die and release the toxin

56
Q

Natural sources of contamination

A

Surface of cut fruit, damaged tissues, skin, GI tract

57
Q

External sources of contamination

A

Air, soil, sewage, water, etc.

58
Q

4 factors that influence microbial growth

A

Temperature, redox potential, pH, water activity

59
Q

For every 10C rise in temp…

A

Catalytic rate of an enzyme doubles

60
Q

Redox potential

A

Measures potential energy difference in a system generated by a coupled reaction
Something is oxidized, something is reduced

61
Q

Redox potential in food is influenced by…

A

Chemical composition, processing treatments, and storage condition

62
Q

Fresh food and plants are in a __ state because….

A

Reduced

BC of the reducing potential of biomolecules (when cell resp stops it changes the redox potential)

63
Q

Why do anaerobes die in the presence of oxygen

A

They lack superoxide dismutase necessary to scavenge toxic oxygen free radicals

64
Q

Controlled atmosphere packaging

A

Atmosphere in storage facility is altered

Hard to do

65
Q

Modified atmosphere packaging

A

Food is enclosed in a high gas barrier packaging material; air is removed from package and flushed with gas(es)

66
Q

Vacuum packaging

A

Removal of air and then sealed

67
Q

Gas flushing

A

Used to extend the life of other products such as fresh pasta, bakery products, cooked eggs and fresh seafood

68
Q

Most bacteria have a pH range of…

A

2-3 units

69
Q

In general, gram pos grow at __ pH than gram neg

A

lower

70
Q

Acids that have a __ dissociation rate are more problematic for bacteria

A

Lower

71
Q

What has a low dissociation rate

A

Weak acids

72
Q

Common acids used in foods

A

Acetic acid, propionic acid, lactic acid, citric acid, sorbic acid, benzoic acid

73
Q

Citric acid

A

Antimicrobial activity is unclear

74
Q

Aw: 0
Aw: 1

A 
0 = dry
1 = pure water
75
Q

Osmophiles

A

Organisms live in high sugar environments

76
Q

Xerophiles

A

Organisms live in very dry environments

77
Q

3 methods for removing water from food

A

Dehydration
Crystallization
Adding solutes (salt, sugar, honey, starch)

78
Q

Hurdle technology

A

Assaults multiple homeostatic processes, most effect when it combines two stressors that act by different mechanisms

Food-Borne Pathogens (14 decks)

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