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Introductory Microbiology > Pathogens > Flashcards

Pathogens Flashcards

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1
Q

What have been a major cause of mortality and morbidity throughout history

A

Infectious disease

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2
Q

The virulence of the organisms differ with

A

Strains

Species

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3
Q

How pathogen is identified

A

The set of virulence genes that carries and expresses

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4
Q

Measure of the ability to cause damage tot he host depends on

A

Invasiness

Toxigenecity

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5
Q

What is invasiness

A

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

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6
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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7
Q

Explain the process of the microorganism pathogenisity in the body

A

Infection process include

1) exposure
2) adherence
3) invasion
4) multiplication

The disease phase

toxicity and invasiveness cause the tissues or systematic damage

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8
Q

What virulence factors are used to invade host tissues

A
  • Adhesins
  • Capsules
  • Enzymes that destroy host tissues
  • Invasins
  • Type 3 secretion systems and type 4 secretion systems
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9
Q

What do adhesins do

A

Promote specific attachment to the host cell surfaces

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10
Q

One adhesin type is usually able to attach to

A

One or a few cell types, dedtermining the site of colonization

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11
Q

What are afimbrial adhesins

A

Glyco/lipo proteins (not filaments) mediate close attachment

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12
Q

What are fimbriae/pilli adhesins

A

Polymers, mediate loose attachment

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13
Q

What is the role of the capsule in bacteria

A

Prevents the pathogen from being destroyed by host immune cells (phagocytes)

Mediates attachment to host cells and to other bacteria

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14
Q

for what type of bacteria capsule is the essential virulence factor

A

Streptococcis pneumoniae

Haemophilus influenzae

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15
Q

Capsule is not only ___

A

Virulence factor (non pathogenic microorganisms may have a capsule too)

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16
Q

What makes the colonies of S.pneumoniae mucoid

A

The capsule

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17
Q

How the penetration of epidermis happens

A

Use a breach in the skin (wounds, surgery, catheter)

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18
Q

How does the penetration of the mucosa happen

A

Destruction of the mucosa: destruction of the single-cell layer or invasion of cells

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19
Q

What is invasion

A

Enter host tissues, multiply, and spread->destruction of host tissues

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20
Q

What is hyaloronidase

A

An enzyme that degrades hyaluronic acid, a sticky polysaccharide that holds host cells together, a component of ECM

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21
Q

What type of bacteria secrete hyaloronidase

A

Staphylococci
Streptococci
Clostridia

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22
Q

What is collagenase

A

Enzyme that degrades the protein collagen present in connective tissues(muscle, cartilage)

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23
Q

Who secretes collagenase

A

Clostridia

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24
Q

What is lecithinase enzyme

A

Degrades lecithin (phosphatidylcholine) in cell membrane -causes the lysis of red blood cells and destroys tissue cells

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25
Q

Clostridium perfingens are (aerobes/anaerobes)

A

Strictly anaerobe

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26
Q

What is gas gangrene

A

Done by Clostridium perfingens

Infection of a deep wound. Uses lecithinase to lyse host cells, collagenase and hyaluronidase to destroy ECM

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27
Q

Describe invasion with hyaluronidase

A

the activity of hyaluronidase causes host
cells to slough apart, allowing pathogens at an initial colonization
site to spread between host cells to attack subsurface tissues

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28
Q

What are hemolysins

A

Cause lysis of red blood cells and a variety of cell types.

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29
Q

What included in hemolysins

A

Some are enzymes (lecithinase, phospholipase), some are cytolysins(pore-forming)

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30
Q

What is alpha-toxin in Staphylococcal

A

Staphylococcal a-toxin is a pore-forming
cytotoxin that is produced by growing Staphylococcus aureus cells. Released as
monomers, seven identical protein subunits oligomerize in the cytoplasmic membrane
of target cells. The oligomer forms a pore, releasing the contents of the cell.

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31
Q

What is leucocidin

A

Causes lysis of leucocytes- white blood cells

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32
Q

Leucocidin is produced by

A

Staphylococci, streptococci and a few Gram-negatives

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33
Q

What are proteases

A

Degrade complement proteins and/or antibodies, produced by several bacteria

34
Q

What is coagulase

A

Causes insoluble fibrin to be deposited on bacterial cells and cloaks the bacteria from the immune system

35
Q

Coagulase produced by

A

Virulent staphylococci

36
Q

After the bacteria formed a coat of insoluble fiber inside the cut, how do they get dispersed

A

They secrete streptokinase that dissolves clot and release pathogen in to the bloodstream

37
Q

What are invasins

A

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

38
Q

What is the major virulence factor of intracellular pathogens

A

Invasins

39
Q

What organisms use invasins

A

Mycobacterium
Salmonella
Listeria
Chlamydia

40
Q

What is the advantage of invasins

A

Invasion of host cells, including phagocytes, protect the bacterial pathogens against the host immune system; good source of nutrients

41
Q

To grow inside host cells, what should be modified

A
  • Block phagosome maturation (block digestion)
  • Increase size of the vacuole
  • Acquire nutrients
  • Block detection of intracellular infection and response (host defense)
42
Q

Who uses T3SS and T4SS

A

Gram-negative pathogens

43
Q

Explain how T3SS functions

A

Forms a channel through the bacterial cytoplasmic membrane, the periplasm, the outer membrane, and the host cell membrane so bacterial proteins can be injected into the host cell cytosol

44
Q

Function of T3SS and T4SS

A
  • Invasion of host cells
  • Block phagosome maturation
  • Take control of host cells
45
Q

The other name for T3SS and T4SS

A

injectosomes

46
Q

what is the difference between T4SS and T3SS

A

T4SS does not have needle-like structure on the tip that is injected in host membrane

47
Q

Is the production of the toxins is necessary for the organism to be highly virulent?

A

No

48
Q

If the organism does not produce toxins, so how the damage can be made

A

By the host’s own immune system or be a result of the large number of pathogens present

49
Q

Bacterial pathogens are associated with two distinct categories of disease

A
  • Infectious diseases (e.g.pneumonia, meningitis, syphilis): result from the pathogen’s growth
  • Intoxication (e.g. food poisoning): result from the presence of a specific toxin
50
Q

Two types of toxins

A

Exotoxins : secreted into the surrounding as the bacterial pathogen grows

Endotoxins: part of the bacterial pathogen

51
Q

Characteristics of exotoxins

A
  • Soluble
  • Usually proteins, usually heat-labile (destroyed by heat)
  • Highly immunogenic (antibody response inactivates exotoxins)
52
Q

When exotoxins are secreted

A

When the organism is lysed

53
Q

Exotoxins are extremely ___

A

Potent, amongst the most lethal substances known

54
Q

How exotoxins are categorized

A 
By the target
-Neurotoxins
-Enterotoxins(GI tract)
-Nephrotoxins (kidney)
-Hepatotoxins(liver)
Etc.
55
Q

What is the power of C. botulinum toxin

A

1 mg neurotoxin can kill 10^6 guinea pigs. 1 pound is enough to kill the entire human population

56
Q

Exotoxins include

A 
Extracellular enzymes (hyaluronidase, etc.)
AB toxins
57
Q

What are AB toxins

A

Modify host cells

58
Q

How AB toxins work

A

Composed of 2 subunit ->enzymatic subunit(A) and binding /cell entry (B)

Subunit A modifies a target inside the host cell leading to damage to the host

Subunit B binds to specific cell receptors providing tissue/ cell type specificity

59
Q

What is the example of A-subunit modification

A

ADP-ribosyltransferase

60
Q

What does the toxin from Clostridium botulinum do

A

Neurotoxin

  • Blocks acetylcholine (no normal muscle contraction) release in neuromuscular junction
  • Flaccid paralysis

“Botox”

  • Reduces wrinkles/frown
  • Muscle spasms
  • Hyperhydrosis(excessive sweating)
61
Q

Clostridium botulinum toxin affect

A

Humans, cattle horses, ducks

62
Q

Clostridium tetanii found in

A

Soil (spore form)

63
Q

What is happening with Clostridium tetanii

A

The bacteria is able to infect puncture wounds and produce the toxin TeNT. The toxin diffuses away, enters the blood stream and acts on neurons

64
Q

Tetanus toxin cause

A

Spastic paralysis: bowed spines, clenched arm and leg muscles, and locked jaws

65
Q

How does Tetanus toxin

A

Muscle relaxation is normally
induced by glycine (G) release from inhibitory interneurons. Glycine acts on the motor
neurons to block excitation and release of acetylcholine (A) at the motor end plate.
(b) Tetanus toxin binds to the interneuron to prevent release of glycine from vesicles,
resulting in a lack of inhibitory signals to the motor neurons, constant release of
acetylcholine to the muscle fibers, irreversible contraction of the muscles, and spastic
paralysis. For the purpose of illustration, the inhibitory interneuron is shown near the
motor end plate, but it is actually in the spinal cord.

66
Q

Infection by Vibrio cholerae is characterized by

A

Severe diarrhea, massive loss of fluid from the intestinal tract

67
Q

What A and B toxins do in Vibrio cholerae

A

There is 5 B parts and 1 A part

B:bind to intestinal cells
A: activate adenylate cyclase, produce cAMP

68
Q

How cholera enterotoxin works

A

Normally, Na+ from lumen goes to the blood and there is no net loss of Cl- movement

Colonization and toxin production by V.cholerae.

Activation of epithelial adenylate cyclase by cholera toxin (cAMP)

Na+ movement blocked, net Cl- movement to lumen

Massive water movement to the lumen; cholera symptoms.

69
Q

What are endotoxins

A

Lipid A of LPS from Gram-negative bacterial pathogens

70
Q

When endotoxins are released

A

During multiplication or lysis of bacterial cells

71
Q

Endotoxins comparing to endotoxisn are (temperature)

A

Heat stable-> cannot be innactivated

72
Q

Is there antobody response against endotoxins?

A

No, weakly immunogenic

73
Q

What is the effect of endotoxins

A

Very effective activator of the immune system, produce general systemic effects: fever, shock, weakness, inflammation, diarrhea; septic shock

74
Q

What is the important cause of syptoms in all Gram-negative bacteria

A

Endotoxins

75
Q

What do exotoxins do with the immune system

A

They are highly antigenic: stimulates the host defense systems to produce antibodies that can neutralize the toxin

76
Q

How vaccines for exotoxins are made

A

-A toxin should be inactivated by heat or formaldehyde

And then inactivated toxoids are injected to induce antibody response

77
Q

WHat are toxoids

A

Toxins that do not have any toxicity , but still cause antibody response

78
Q

The example of the vaccine that is done though toxoids

A

diphteria toxin (DTaP)

79
Q

Is there a vaccine against endotoxin?

A

No, because they cannot be inactivated by heat or formaldehyde and converted to taxoid

80
Q

What is pathogenicity islands

A

Section of the chromosome encoding virulence factors

Several genes that encode these virulence factors are found clustered together on the chromosome as pathogenicity islands

The type of fimbriae, enzymes for penetration encoded on the choromose

81
Q

In what bacteria pathogenicity islands are found

A

Salmonella enterica and related gram-negative pathogens such as pathogenic strains
of Escherichia coli

Introductory Microbiology (21 decks)

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