damage by bacterial pathogens Flashcards

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1
Q

Mechanisms that damage the host during infections

A

cell death
damage by host responses
toxins

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2
Q

host cell death caused by?

A

growth of pathogen in cells
cell mediated immunity
membrane damaging toxins

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3
Q

growth of pathogen within host cells and damage to host cell

A

Cell membrane damage causes cell death (free radicalinduced lipid peroxidation).
• Damage is proportional to number of bacteria inside cell.

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4
Q

cell-mediated immunity and cell death

A

indirectly caused by pathogen, infection recognized via CD8 and MHC= cell killed

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5
Q

Membrane-damaging toxins

A

lead to apoptosis

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6
Q

Damage caused by host responses

A

Uncontrolled inflammation
Inflammation – healthy response
- increased blood supply (redness)
- increased vascular permeability (edema)
- chemotaxis (infiltration by phagocytes and lymphocytes
due to exaggerated adaptive immune response = hypersensitivities

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7
Q

type I hypersensitivity, can lead to?

A

Th2, IgE, mast cells

allergy but can lead to anaphylaxis and shock

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8
Q

Type II hypersensitivity

A

bound antibodies leading to complement and leukocyte activation against cell surfaces/ extracellular matrix

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9
Q

Type III hypersensitivity

A

bound antibodies leading to complement and leukocyte activation to soluble molecules, then immune complex deposition into vascular membrane

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10
Q

Type IV hypersensitivity

A

inflammation by purely CMI responses (not antibodies)

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11
Q

Toxins

A

Microbial product or component that can injure another cell or organism at low concentrations usually altering host metabolism

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12
Q

mechanisms of toxin action (where they can operate?)

A

Modulation of targets inside a host cell
Action in the extracellular matrix
Action on surface of a host cell

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13
Q

variation in toxin production and disease conseuqnces

A

Toxin production and disease consequences vary widely

among pathogenic bacteria

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14
Q

transfer of toxin genes

A

Like transposons, many toxin-encoding genes are carried
on plasmids or temperate bacteriophage genomes (easy to
transfer to other, non-toxigenic bacteria).

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15
Q

CTXφ (a bacteriophage) and Vibrio cholerae

A

ctxA and ctxB encode the
proteins that comprise
cholera toxin

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16
Q

types of toxins causing Modulation of targets inside a host cell

A

Exotoxins

Type III cytotoxins

17
Q

exotoxins

A

secreted by pathogen via type I and II systems

18
Q

Type III cytotoxins

A

injected into host cells contact-dependent

19
Q

Common features of exotoxins

A
  1. A-B toxins (2 components)
  2. Require activation (proteolysis or reduction of disulfides)
  3. Many are ADP-ribosyltransferases
20
Q

ADP-ribosyltransferases

A

take the ADP ribose from NAD and add to a target protein in the host cell thus inactivating it

21
Q

AB exotoxins

A

B domain is the binding domain
A is the enzymatic (active) domain

B domain also mediates the entry of the A domain into the host cell
• only A enters cell for some toxins
• A and B enter cell for other toxins

22
Q

Action of diphtheria toxin (an exotoxin)

A
23
Q

toxins with Action on surface of a host cell

A

membrane damaging toxins
super Ag
endotoxins

24
Q

types of Membrane-damaging toxins

A

lipases, pore-forming toxins, hemolysins

25
Q

Endotoxin example

A

LPS, specifically lipid A

26
Q

endotoxin in small vs large amounts

A
27
Q

toxins with Action in the extracellular matrix

A

Exoenzymes:
collagenases
hyaluronidases
DNases: break down viscous DNA left by dead cells
streptokinase (Streptococcus pyogenes): activates plasminogen (converts to plasmin) help microbes spread

28
Q

Protection against exotoxins

A

A. Immunization with toxoids

B. Treatment with antitoxins passive immunization