Bacterial toxins

Question 1

Why do bacteria use toxins?

Answer 1

As virulence factors to cause host damage

Question 2

What are the 2 classes of toxins?

Answer 2

Endotoxins

Exotoxins

Question 3

Describe the structure of endotoxins?

Answer 3

• Cell wall related toxin 
• Innate part of the cell called lipopolysaccharide
• LPS Made up of
	a. O-polysaccharide
	b. Core polysaccharide
	c. Lipid A= this is the endotoxin component 
• Low site specificity 
• Integral bacterial components

Question 4

Where are endotoxins released from?

Answer 4

From lysed or damaged cells

Question 5

What are the 3 types of exotoxins?

Answer 5

Pore forming toxin
Enzymatic activity toxin
Super antigens

Question 6

What is an example of a pore forming toxin?

Answer 6

Pneumolysin

Question 7

What is an example of a Enzymatic activity toxin?

Answer 7

AB toxin

Question 8

What are examples of a Super antigen?

Answer 8

Toxic shock syndrome toxin

Streptococcal pyrogenic exotoxins

Question 9

What is the MOA of Superantigens?

Answer 9

Bypass t cell activation and its cascade of events
Cause massive inflammatory reaction

bind MHC II molecules
Activate large T cell number- 1 in 5
Release cytokine IL2
Bypasses complex cascade = no t cell activation and cytokine storm

Question 10

What produces Toxic shock syndrome toxin and what are the signs and symptoms?

Answer 10

Produced by staphylococcus aureus
Involves multiple organ systems
Signs and symptoms: fever, hypotension, rash, desquamation of soles and palms

Question 11

What are the types of AB toxins?

Answer 11

Diphtheria toxin

Botulinum toxin- BoNT

Question 12

What produces diphtheria toxin?

Answer 12

Corynebacterium diphtheriae

Question 13

Describe the microbiology of Corynebacterium diphtheriae and the effects of the Diphtheriae toxin produced?

Answer 13

○ Gram +Ve
○ Non-motile
○ Clubbed morphology
○ Pseudo membrane formation in throat= causes diphtheria
○ Swallowing difficulty
○ Systemic effects: heart complication, coma, death

Question 14

What is the MOA of Diphtheriae toxin?

Answer 14

Targets protein translocation
Aerosol inhaled
Colonises throat
 Single chain AB diphtheriae toxin produced
Inhibits EF2 in eukaryotic cells
Inhibits protein synthesis
Pseudomrmnrane formed in throat

Question 15

What is the treatment option for Diphtheriae?

Answer 15

6 in 1 toxoid vaccine

Question 16

What produces Botulinum toxin?

Answer 16

clostridium botulinum

Question 17

Describe the microbiology of clostridium botulinum and the effects of the Botulinum toxin produced?

Answer 17

Enters blood stream by ingested spores which colonise GIT, wound contaminated with spores, contaminated food
Gram +ve
Motile
Rod
Obligate anaerobe
Sub terminal spores
Causes botulism= toxin mediated disease causing flaccid paralysis due to effect of toxin on peripheral nervous system

Question 18

What is the MOA of Botulinum toxin?

Answer 18

Causes loss of excitatory pathway
1 of 3 SNARE proteins cleaved at NMJ
Blocks Ach release 
Blocks NM transmission
Mo muscle contraction
Irreversible muscle relaxation and flaccid paralysis

Question 19

What are the signs and symptoms of botulism?

Answer 19

Blurred vision
Speaking difficulty 
Diarrhoea
Vomiting
Paralysis

Question 20

What bacteria produce pore forming toxins?

Answer 20

Streptococcus pneumoniae
Group A streptococci
Escherichia coli
Staphylococcus aureus

Question 21

What is the MOA of pore forming toxins?

Answer 21

Cytotoxic effects
Oligomerise in host membrane to form pores

○ Secreted as H2O soluble molecule
○ Recognise and bind specific target membrane receptor
○ Form multimers
○ Undergo conformational change
○ Aq pore forms in membrane
○Some toxins dissociate some remain associated with receptor

Question 22

What bacteria produce Pneumolysin?

Answer 22

streptococcus pneumoniae

Question 23

Describe the microbiology of streptococcus pneumoniae?

Answer 23

○ Gram +ve coccus
○ 90 capsular types
○ Non-motile

Question 24

Describe the production of Pneumolysin in CAP?

Answer 24

It is a cytolytic cholesterol dependent toxin
Colonises lungs and causes histopathical change
Early immunosuppressive CAP= mucociliary pathway inhibited, macrophage apoptosis
Proinflammatory late CAP= neutrophil influx, complement activation, ROS production, inflammatory mediated tissue damage
Signs and symptoms of CAP: fever, malaise, dyspnoea, productive cough, purulent discharge, wheeze, chest crackle

Question 25

What bacteria produces more than one type of toxin that leads to pertussis/whooping cough?

Answer 25

Bordetella pertussis

Question 26

What toxins are produced by Bordetella pertussis and what are their MOAs?

Answer 26

1. Pertussis toxin- enzymatic activity toxin
    Immune inhibition due to reduced neutrophil recruitment
2. Tracheal Cytotoxin = endotoxin
    Mucociliary pathway inhibition
3. Adenylate cyclase toxin= pore forming and enzymatic activity toxin
    Immune inhibition- t cell and phagocytosis

Question 27

Describe the microbiology of Bordetella pertussis?

Answer 27

Gram -ve
Aerobic
Cocco-bacillus
Confined to humans

Question 28

What are the signs and symptoms of pertussis?

Answer 28

Paroxysms of cough
Secondary pneumonia
High mortality in <4 years old

Question 29

Describe how the 6 in 1 toxoid vaccine works?

Answer 29

Exploits use of toxins by using their targets

Question 30

What are the other Treatments/prevention for toxin mediated disease?

Answer 30

vaccine use for diphtheria and wherever possible
Antibiotic management
Anti-toxins as post exposure prophylaxis

Question 31

What is the MOA of anti-toxins?

Answer 31

Neutralises toxin effects in the blood