damage by bacterial pathogens

Question 1

Mechanisms that damage the host during infections

Answer 1

cell death
damage by host responses
toxins

Question 2

host cell death caused by?

Answer 2

growth of pathogen in cells
cell mediated immunity
membrane damaging toxins

Question 3

growth of pathogen within host cells and damage to host cell

Answer 3

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

Question 4

cell-mediated immunity and cell death

Answer 4

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

Question 5

Membrane-damaging toxins

Answer 5

lead to apoptosis

Question 6

Damage caused by host responses

Answer 6

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

Question 7

type I hypersensitivity, can lead to?

Answer 7

Th2, IgE, mast cells

allergy but can lead to anaphylaxis and shock

Question 8

Type II hypersensitivity

Answer 8

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

Question 9

Type III hypersensitivity

Answer 9

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

Question 10

Type IV hypersensitivity

Answer 10

inflammation by purely CMI responses (not antibodies)

Question 11

Toxins

Answer 11

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

Question 12

mechanisms of toxin action (where they can operate?)

Answer 12

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

Question 13

variation in toxin production and disease conseuqnces

Answer 13

Toxin production and disease consequences vary widely

among pathogenic bacteria

Question 14

transfer of toxin genes

Answer 14

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

Question 15

CTXφ (a bacteriophage) and Vibrio cholerae

Answer 15

ctxA and ctxB encode the
proteins that comprise
cholera toxin

Question 16

types of toxins causing Modulation of targets inside a host cell

Answer 16

Exotoxins

Type III cytotoxins

Question 17

exotoxins

Answer 17

secreted by pathogen via type I and II systems

Question 18

Type III cytotoxins

Answer 18

injected into host cells contact-dependent

Question 19

Common features of exotoxins

Answer 19

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

Question 20

ADP-ribosyltransferases

Answer 20

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

Question 21

AB exotoxins

Answer 21

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

Question 22

Action of diphtheria toxin (an exotoxin)

Answer 22

Question 23

toxins with Action on surface of a host cell

Answer 23

membrane damaging toxins
super Ag
endotoxins

Question 24

types of Membrane-damaging toxins

Answer 24

lipases, pore-forming toxins, hemolysins

Question 25

Endotoxin example

Answer 25

LPS, specifically lipid A

Question 26

endotoxin in small vs large amounts

Answer 26

Question 27

toxins with Action in the extracellular matrix

Answer 27

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

Question 28

Protection against exotoxins

Answer 28

A. Immunization with toxoids

B. Treatment with antitoxins passive immunization