Pathogens and Hosts

Question 1

Make a list of the signs and symptoms that someone has an infection./

Answer 1

inflammation
pain
pyrexia
tachycardia
rigors
increased white cell count
Increased C reactive protein (CRP)

Question 2

What is a pathogen?

Answer 2

an organism which can cause disease

Question 3

What is a commensal?

Answer 3

s an organism which is part of normal flora e.g. E. coli in the gut, Staph aureus in the nose, axilla

Question 4

What can be an issue between pathogens and commensal?

Answer 4

The distinction between these is not always clear

Question 5

What can be used to determine whether a microorganism causes a disease?

Answer 5

Koch’s Postulates

Question 6

What does Koch’s Postulates state a microorganism should be able to do in order to cause a disease?

Answer 6

organism must be found in all cases of the disease
able to be cultured outside the body for several generations
should reproduce the disease on inoculation

Question 7

What is pathogenicity?

Answer 7

The capacity of a micro-organism to cause an infection

Question 8

What are the requirements of The capacity of pathogenicity?

Answer 8

Infectivity
Virulence

Question 9

What does infectivity mean?

Answer 9

Ability to become established.

Question 10

What does virulence mean?

Answer 10

Ability to cause harmful effects once established

Question 11

Define Infectivity

Answer 11

Ability to become established on or within a host

Question 12

How does E.coli demonstrate infectivity?

Answer 12

Receptor on uroepithelial cells

Question 13

What is virulence conferred by?

Answer 13

Virulence factors.

Question 14

List some virulence factors.

Answer 14

Invasiveness
Toxin production
Evasion of immune system

Question 15

What is virulence specific to?

Answer 15

Strains not species

Question 16

How are exotoxins released?

Answer 16

Extracellularly by the micro-organism

Question 17

What are enterotoxins?

Answer 17

exotoxins which act on the GI tract

Question 18

What is endotoxin structurally part of?

Answer 18

Gram negative cell wall

Question 19

What are super antigens able to do?

Answer 19

Able to stimulate division of T cells in the absence of specific antigen

Question 20

What does overwhelming cytokine production cuase?

Answer 20

Toxic shock

Question 21

Give an example of an endotoxin

Answer 21

Lipopolysaccharide-
1. Lipid A
2.Oligosaccharide core
3.Specific polysaccharide chain

Question 22

What reponses do endotoxins produce?

Answer 22

Cytokine production
Fever, rigors, hypotension, tachycardia, collapse

Question 23

What are the three characteristics of virus pathogenic mechanisms?

Answer 23

Cell destruction following virus infection
Virus-induced changes to cellular gene expression
Immunopathogenic disease

Question 24

Describe cell destruction following virus infection

Answer 24

Death of T4+ cells by HIV

Question 25

Describe Virus-induced changes to cellular gene expression

Answer 25

Cellular transformation by tumour viruses.

Question 26

Give two examples of Immunopathogenic disease

Answer 26

Influenza A virus. Coxsackievirus-induced myocarditis.

Question 27

Name some sites of viral entry.

Answer 27

Respiratory tract Alimentary tract Urinogenital tract Conjunctiva Arthropod Skin Capillary

Question 28

Describe acute infection.

Answer 28

Virus increases and decreases.

Question 29

Describe latent infection.

Answer 29

Virus increases and then decreases so is unnoticed but does not fully go away. Increases in the future.

Question 30

Describe chronic infection.

Answer 30

Virus increases, may decrease slightly but then stays the same.

Question 31

Describe tumour virus infection.

Answer 31

Slight increase in early disease but then decreases and stays constant before rapidly spiking in the future. Separated into early and late disease.

Question 32

Name two acute viruses.

Answer 32

Influenza A virus Enterovirus

Question 33

Discuss acute virus infection.

Answer 33

Localised to specific site of body Development of viraemia with widespread infection of tissues.

Question 34

Give an example of a latent virus infection.

Answer 34

Herpes simplex virus

Question 35

Explain how a latent virus infection of herpes may come back.

Answer 35

Primary infection of epithelial cells. Virus migration to the ganglia. Virus remains latent in nucleus (No Virus Replication.) Stimuli (e.g. sunlight) reactivates virus. Virus migration to epithelial cells leading to virus replication.

Question 36

Name two tumour virus infections.

Answer 36

Papillomaviruses (HPV) Retroviruses

Question 37

Don't hate me but describe the process of retrovirus replication

Answer 37

I'M SORRY After a retrovirus enters a host cell, reverse transcriptase converts the retroviral RNA genome into double-stranded DNA. This viral DNA then migrates to the nucleus and becomes integrated into the host genome. Viral genes are transcribed and translated. New virus particles assemble, exit the cell, and can infect another cell.

Question 38

How can retroviruses cause a tumour?

Answer 38

Virus infects cell. Virus nucleic acid, as DNA, integrates into cellular genome. Virus causes changes in cellular gene expression. Uncontrolled cell multiplication and tumour formation.