17 - Bacterial Pathogenesis

Question 1

Bacteria which commonly have afimbrial adhesins

Answer 1

G- bacteria (as are often inserted in outer cell membrane)

Question 2

Proportion of microbiome that is in large intestine

Answer 2

~70%

Question 3

Protein that ETEC uses to bind to human intestinal epithelium

Answer 3

CS3

Question 4

Experiment looking at ETEC virulence in piglets

Answer 4

Without K88 adhesin, there was no ETEC adhesion to intestinal wall, an no pathogenesis, even in E coli that were toxin+ (no diarrhoea)

Question 5

How can piglets be immunised?

Answer 5

Immunise sow, when piglets suckle milk get sow’s IgA

Question 6

Travelan

Answer 6

Antibodies against ETEC.

Treats traveller’s diarrhoea

Question 7

Where do yersinia enter intestinal wall?

Answer 7

Through M cells

Question 8

Which protein does yersinia use to enter M cells?

Answer 8

Invasin

Question 9

What does yersinia invasin bind to?

Answer 9

Integrin on M cell

Question 10

What are pyogenic bacteria?

Answer 10

Pathogenic bacteria that evade phagocytosis, resulting in pus formation

Question 11

Example of bacterium which produces leukocidins

Answer 11

S pyogenes, S aureus

Question 12

Example of a bacterium that produces an anti-inflammatory

Answer 12

Choleratoxin is an anti-inflammatory agent

Question 13

Number of S. pneumoniae capsular antigens

Answer 13

Around 90

Question 14

Is there any cross-reactivity between Ig against S. pyogenes capsules?

Answer 14

No

Question 15

Adult pneumococcal vaccine

Answer 15

23 most-common S. pyogenes capsular antigens

Question 16

Children’s’ pneumococcal vaccine

Answer 16

13 most-common S. pyogenes capsular antigens

Question 17

How can capsulated bacteria be opsonised?

Answer 17

Anti-capsular antigen Ig binds, and complement binds to Ig Fc region

Question 18

Most important type of meningococcus worldwide

Answer 18

Type A

Question 19

Most important type of meningococcus in Australia

Answer 19

Type B

Question 20

Example of a bacterium with an non-antigenic capsule

Answer 20

Meningococcus type B

Question 21

Stages of phagocytosis
1)
2)
3)
4)
5)
6)

Answer 21

1) Chemotaxis
2) Attachment
3) Metabolic burst
4) Ingestion
5) Phagolysosome formation
6) Destruction

Question 22

Some strategies used by bacteria to evade destruction by phagocytes
1)
2)
3)
4)

Answer 22

1) Inhibit respiratory burst
2) Prevent phagolysosome formation
3) Escape from phagocytic vacuole
4) Resist bactericidal systems

Question 23

C’ pathway activated by LPS

Answer 23

Alternative pathway

Question 24

Non-professional phagocytes

Answer 24

Cells that need to be induced to plagocytose.

EG: With SIP proteins

Question 25

Substrate of lysozyme

Answer 25

Beta1-4 linkage in peptidoglycan

Question 26

Why are newborn babies a risk group for tetanus infection?

Answer 26

Some cultures cover necrotising umbilical cord with cow dung. C tetani lives in cow faeces (and faeces of other animals), colonises necrotising tissue.

Question 27

Only way that you can get anti-tetanustoxin Ig

Answer 27

Immunisation. The amount of tetanospasmin required for Ig production in a natural infection would kill you.

Question 28

How can replicating bacteria release endotoxin?

Answer 28

Some G- bacteria release bits of cell wall

Question 29

Pyrogen free

Answer 29

Autoclaving won’t inactivate endotoxin. Pyrogen free means endotoxin has been removed

Question 30

Heat resistance of endotoxin

Answer 30

High

Question 31

Ways to overcome adaptive immune system
1)
2)
3)
4)

Answer 31

1) Direct immunosuppression
2) Expression of weak antigens
3) Antigenic diversity
4) Antigen modification

Question 32

Chemical nature of exotoxin

Answer 32

Protein

Question 33

Chemical nature of endotoxin

Answer 33

LPS

Question 34

Antigenicity of exotoxin versus endotoxin

Answer 34

Exotoxin highly antigenic. Endotoxin variable

Question 35

Specificity of exotoxin versus endotoxin

Answer 35

Exotoxin very specific. Endotoxin non-specific (as induces immune response)

Question 36

Broad division of bacterial exotoxin modes of action

Answer 36

1) Cytotoxic (inhibitory), EG leukocidins

2) Cytotonic (excitatory), EG choleratoxin

Question 37

Examples of intracellularly acting, cytotoxic exotoxins
1)
2)

Answer 37

1) Diphtheriatoxin

2) Shigatoxin

Question 38

Example of a simple exotoxin

Answer 38

Heat-stable enterotoxin

Question 39

Shigatoxin receptor

Answer 39

gb3

Question 40

SHigatoxin mechanism

Answer 40

A1 subunit modifies 28S rRNA of 60S ribosomal subunit, prevents protein synthesis