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Microbiology Final > Pathogens Host Defenses > Flashcards

Pathogens Host Defenses Flashcards

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Biology 101 flashcards
1
Q

What are pathogens?

A

Microorganisms capable of causing disease/damage to the host.

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2
Q

Do all strains of one species have the same ability to cause disease?

A

No

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3
Q

What is a pathogen usually identified by?

A

The set of virulence genes that it carries and expresses

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4
Q

What is virulence?

A

A measure of the ability to cause damage to the host

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5
Q

What 2 factors is virulence determined by?

A

Invasiveness, toxigenicity

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6
Q

What is invasiveness?

A

The ability of microorganisms to become established in the host, or overcome the host defenses and to spread in the tissues

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7
Q

What is toxigenicity?

A

the capacity of the microorganism to produce substances known as toxins that damage specific tissues of the host

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8
Q

What happens once a host is exposed to a pathogen? 5 steps

A
  1. Adherence to skin or mucosa
  2. Invasion through epithelium
  3. Growth and colonization (production of virulence factors)
  4. Toxicity or Invasiveness
  5. Tissue damage, disease
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9
Q

What are the 5 different types of virulence factors that pathogens use to invade host tissues?

A
  1. adhesins
  2. capsules
  3. enzymes that destroy host tissues
  4. Invasins
  5. Type 3 Secretion Systems (T3SS) and Type 4 Secretion Systems (T4SS)
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10
Q

What do adhesins promote?

A

Specific attachment to host cell surfaces

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11
Q

How many cell types is one adhesin normally able to attach to?

A

one or many

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12
Q

What are Fimbriae/Pili? What do they mediate?

A

Polymers that mediate loose attachment

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13
Q

What are Afimbrial adhesins?

A

(not filaments) mediate close attachment

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14
Q

In what 2 ways do capsules aid pathogens?

A
  1. They prevent them from being destroyed by host immune cells (phagocytes)
  2. They help them attach to host cells and to other bacteria
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15
Q

What are 2 essential virulence factors for some bacterial pathogens?

A

Streptococcus pneumonia, Haemophilus influenzae

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16
Q

What is epidermis?

A

The outer layer of skin

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17
Q

How do most pathogens infect humans?

A

They penetrate the epidermis by using breaches in the skin (wounds, surgery, catheter)

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18
Q

What happens when pathogens penetrate the mucosa?

A

They destroy the single-cell layer or invade the cells themselves

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19
Q

What is hyaluronidase? Function?

A

An extracellular enzyme that degrades hyaluronic acid

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20
Q

Which pathogens release hyaluronidase?

A

Staphylococci, streptococci, clostridia

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21
Q

What is hyaluronic acid?

A

A sticky polysaccharide that holds host cells together

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22
Q

What is collagen? Function?

A

An extracellular enzyme that degrades the protein collagen present in connective tissues (muscle, cartilage)

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23
Q

What is the function of lecithinase? Causes the lysis of what?

A

An extracellular enzyme that degrades lecithin (phosphatidylcholine) in cell membranes – causes the lysis of RBCs and destroys tissue cells

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24
Q

What is gas gangrene?

A

The term used to describe the decay or death of an organ or tissue caused by lack of blood supply in wounds infected by anaerobic bacteria

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25
Q

What microorganism are present in gas gangrene? What do they do?

A

Clostridium perfringens. They break down tissue by gas production.

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26
Q

What type of microorganism are Clostridium perfringens?

A

strict anaerobes

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27
Q

What enzyme do Clostridium perfringens use to lyse host cells in gas gangrenes? What enzymes do they use to destroy the extracellular matrix?

A

Lecithinase

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28
Q

What are hemolysins? What are the different types of hemolysins?

A

A substance in the blood that destroys RBCs and liberates hemoglobin.

Enzymes, cytolysins

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29
Q

What are two examples of hemolysin enzymes?

A

Lecithinase, phospholipase

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30
Q

What is a characteristic of hemolysin cytolysins?

A

Pore-forming

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31
Q

What does the release of the extracellular enzyme leucocidin target & cause the lysis of?

A

Leucocytes (white blood cells) produced by staphylococci, streptococci, and some gram neg bacteria

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32
Q

What are leucocytes?

A

White blood cells

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33
Q

What do the extracellular proteins, Proteases, do once they are released?

A

The degrade complement proteins and/or antibodies

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34
Q

What produces the extracellular enzyme coagulase?

A

virulent staphylococci

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35
Q

What do coagulase enzymes cause? What does this do?

A

insoluble fibrin to be deposited on bacterial cells. This blocks the bacteria from the immune system

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36
Q

What are invasins?

A

Surface proteins, or injected proteins, that allow microorganisms to enter cells (invade host cells)

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37
Q

What is one major virulence factor of intracellular pathogens?

A

Invasins

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38
Q

How does the invasion of host cells benefit bacterial pathogens?

A

It protects them against the host immune system and is a good source of nutrients

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39
Q

What are 4 examples of pathogens that have invasins?

A

Mycobacterium, Salmonella, Listeria, Chlamydia

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40
Q

In what 4 ways do pathogens modify the properties and behaviors of host cells in order for them to grow inside of host cells?

A
  1. block phagosome maturation (block digestion)
  2. Increase size of vacuole
  3. Acquire nutrients
  4. Block detection of intracellular infection and response (host defense)
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41
Q

What is a phagosome?

A

a vacuole in the cytoplasm of a cell, containing a phagocytosed particle enclosed within a part of the cell membrane.

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42
Q

What two type of secretion systems do a lot of gram-negative pathogens use?

A

Type 3 (T3SS) and Type 4 (T4SS)

43
Q

What does a T3SS do?

A

It forms a channel through the bacterial cytoplasmic membrean + periplasm + outer membrane + host cell membrane so bacterial proteins can be injected into the host cell cytosol

44
Q

What are the 3 functions of T3SS?

A
  1. Invasion of host cells
  2. Block phagosome maturation
  3. Take control of host cells
45
Q

How is T4SS different from T3SS?

A

T4SS does not have a needle-like structure

46
Q

What are T3SS and T4SS’s also called?

A

injectisomes

47
Q

What are toxins?

A

Extracellular enzymes that cause damage

48
Q

Is toxin production always necessary for an organism to be highly virulent? What else can be the cause of damage to an organism?

A

No. Damage can be caused by the host’s own immune system or be a result of the large # or pathogens present

49
Q

What are the 2 categories of diseases that bacterial pathogens are associated with?

A
  1. Infectious diseases

2. Intoxications

50
Q

What do infectious disease result from?

A

The pathogen’s growth

51
Q

What do intoxication’s result from?

A

The presence of a specific toxin

52
Q

What are 3 examples of infectious diseases?

A

Pneumonia
Meningitis
Syphilis

53
Q

What is an examples of an intoxication?

A

food poisoning

54
Q

What 2 categories are toxins divided into?

A

Exotoxins & endotoxins

55
Q

What is an exotoxin?

A

A toxin secreted into the surroundings as the bacterial pathogen grows

56
Q

What is an endotoxin?

A

A toxin that is part of the bacterial pathogen

57
Q

Are exotoxins soluble or insoluble?

A

soluble

58
Q

When are exotoxins secteted/released?

A

When the organism is lysed

59
Q

What macromolecule are exotoxins normally?

A

Proteins

60
Q

What destroys exotoxins?

A

Heat (heat-liable)

61
Q

What inactivates exotoxins? Exotoxins are highly what?

A

Antibody response inactivates exotoxins. They are highly immunogenic (produce an immune response)

62
Q

What are exotoxins categorized by? Give 5 examples.

A

Their target.

  1. Neurotoxins (nerve tissue)
  2. Enterotoxins (GI tract)
  3. Nephrotoxins (kidney)
  4. Hepatotoxins (liver)
  5. Cardiotoxins (heart)
63
Q

What are 2 examples of extracellular exotoxins?

A

Hyaluronidase, collagenase

64
Q

What type of toxin are AB toxins?

A

Exotoxins

65
Q

What do AB toxins do? What 2 subunits are they made up of?

A

They modify host cells. Enzymatic subunit A + binding/cell entry B

66
Q

What does Subunit A of AB toxins do?

A

It modifies a target inside the host cell, leading to damage to the host.

67
Q

What is an example of an enzymatic subunit A of an AB toxin?

A

ADP-ribosyltransferase

68
Q

What does Subunit B of AB toxins do? What does this provide?

A

It binds to specific cell receptors providing tissue/cell type specificity

69
Q

What is an example of an AB toxin? What category of an AB toxin does it fall under?

A

Clostridium botulinum, a neurotoxin

70
Q

What does the Botulinum neurotoxin block? What is the effect?

A

Blocks acetylcholine release in neuromuscular junction, leading to Flaccid paralysis (this inhibits muscle contractions)

71
Q

What organisms does the AB neurotoxin Botulunim affect?

A

Humans
Cattle
Horses
Ducks

72
Q

In what silly way do humans use the Botulinum toxin?

A

BOTOX!

73
Q

What does BOTOX do?

A
  • Reduces wrinkles / frown
  • Controls muscle spasms
  • treats for hyperhydrolysis (excessive sweating)
74
Q

What does the acetylcholine neurotransmitter normally do? How does the botulism toxin affect this?

A

It induces contraction of muscle fibers.

Botulism toxin blocks the release of A, inhibiting contraction

75
Q

What is an example of an AB5 toxin?

A

Cholera toxin (Vibrio cholerae)

76
Q

What is an infection by the cholera toxin Vibrio cholerae characterized by?

A

Severe diarrhea

Massive loss of fluid from the GI tract

77
Q

In the cholera toxin (Vibrio cholerae), what is the function of the A subunit? B subunit?

A

A: Adenylate cyclase, produces cAMP

B: binds to intestinal cells

78
Q

When is lipid A of LPS from gram-neg bacterial pathogens released?

A

During multiplication of lysis of bacterial cells

79
Q

Can endotoxins be inactivated? Why?

A

No, heat stable

80
Q

Are endotoxins strongly or weekly immunogenic? How?

A

Weakly - no antibody are produced agains LPS

81
Q

Endotoxins are very effective activators of what? What do they produce?

A

The immune system. They produce general systemic effects such as pyrogenic (heat) fever, shock, weakness, inflammation, diarrhea, septic shock

82
Q

Endotoxins are an important cause of symptoms in what type of bacterial infections? What are 2 exmples?

A

In all gram-neg

Salmonella, E.coli

83
Q

Exotoxins stimulate the host defense system to produce what? This makes them highly what?

A

Antibodies that can neutralize the toxin.

Highly antigenic

84
Q

When you get a vaccine, what is actually injected into your body?

A

Toxoids

85
Q

Can exotoxins or endotoxins become toxoids?

A

Exotoxins only

86
Q

What are toxoids?

A

ENXOtoxins inactivated by heat or formaldehyde

87
Q

What characteristic of exotoxins do toxoids still possess?

A

Toxoids are no longer toxic, but are still antigenic (induce antibody response)

88
Q

Why can endotoxins not be converted into toxoids?

A

They cannot be inactivated by heat or formaldehyde

89
Q

Are there any vaccines against endotoxins?

A

No, because can not be transformed into toxoids

90
Q

What are the chemical properties of exotoxins?

A

Proteins excreted by certain gram-positive or gram-negative bacteria; generally heat-liable

91
Q

What are the chemical properties of endotoxins?

A

Lipopolysaccharide-lipoprotein complexes, released on cell lysis as part of the outer membrane of gram-negative bacteria; extremely heat-stable

92
Q

What is the mode of action/symptoms of exotoxins?

A

Specific; usually binds to specific cell receptors or structures; either cytoyoxin, enterotoxin or neurotoxin with defined, specific action on cells or tissues

93
Q

What is the mode of action/symptoms of endotoxins?

A

General; fever, diarrhea, vomiting

94
Q

What is the toxicity of exotoxins?

A

Often highly toxic, sometimes fetal

95
Q

What is the toxicity of endotoxins?

A

Weakly toxic, rarely fatal

96
Q

What is the immunogenicity response of exotoxins?

A

Highyl immunogenic; stimulate the production of neutralizing antibody (antitoxin)

97
Q

What is the immunogenicity response of endotoxins?

A

Relatively poor immunogen; immune response not sufficient to neutralize toxin

98
Q

What is the toxoid potential of exotoxins?

A

Treatment of toxin with formaldehyde will destroy toxicity, but treated toxin (toxoid) remains immunogenic

99
Q

What is the toxoid potential of endotoxins?

A

None

100
Q

What is the fever potential of exotoxins?

A

Does not produce fever in host

101
Q

What is the fever potential of endotoxins?

A

Pyrogenic (heat), often induces fever in host

102
Q

What are pathogenicity islands?

A

the section of the chromosome encoding virulence factors

103
Q

Slide 26

A

Host defenses

Microbiology Final (3 decks)

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