Virulence and virulence factors

Question 1

What is pathogenesis?

Answer 1

mechanism of disease

Question 2

What is pathogenicity?

Answer 2

ability to cause disease

Question 3

What is virulence?

Answer 3

degree of pathogenicity

Question 4

LD50

Answer 4

dose needed to kill 50% sample
(LD = lethal dose)

Question 5

ID50

Answer 5

dose to infect 50% sample

Question 6

What are the limitations of LD50 and ID50?

Answer 6

-measured in model systems, not necessarily same in humans
-reflect cumulative contribution of many steps within disease process
-values can be misleading (ie. severity of disease not reflected)

Question 7

What alters bacteria virulence?

Answer 7

-invasiveness of the bacteria (whether it can get into niche and survive and replicate there) (transmissibility, adherence, nutrient acquisition, etc)
-damage bacteria causes (toxins, enzymes)

Question 8

What are virulence factors?

Answer 8

bacterial products that contribute to pathogenicity
-lots of virulence involved in pathogenicity (diff factors in diff steps)

Question 9

How can pathogenesis be studied?

Answer 9

phenotypic readouts (measuring a property, eg. toxin acitivity)
studying gene contribution to that phenotype

Question 10

How can phenotypic readouts be used to study pathogenesis?

Answer 10

-use model organism (typically mouse, etc -must choose ethically, practically and cost-efficiently) to observe disease (may be diff sim species or diseases)
-identify and study virulence factors

Question 11

What alternatives are there to using animal models to study pathogenesis phenotypically?

Answer 11

-cell lines (simpler, more ethical, but only shows one cell line so doesn’t mimic whole disease) -> used to study adherence, invasion, toxicity
-organoids (simpler, more ethical, can show multiple cell types and 3D architecture, doesn’t mimic whole disease

Question 12

What tools can be used to study virulence factors?

Answer 12

-using immunological tools, like antibodies against specific proteins
-using biochem tools, such as purifying protein and observing phenotype
-using genetic tools -over-expressing or knocking out genes (gain or loss of funct observed)

Question 13

How can targetted mutagenesis be carried out?

Answer 13

-specific disruption (insertion into ORF)
-specific deletion of target gene

-subtler changes: alter DNA seq

Question 14

How can random mutagenesis be carried out?

Answer 14

-chem mutageneis
-radiation

-transposons

Question 15

What are the advantages of using cell lines to study pathogenesis?

Answer 15

-less ethical issues
-simpler, cheaper, easier to scale, more variable

Question 16

What are the disadvantages of using cell lines to study pathogenesis?

Answer 16

-only model 1 cell line
-only mimics aspects of disease
-immortalised cell lines different to original tissue
-specialised growth conditions affect bact behaviour

Question 17

What are the advantages of using organoids to study pathogenesis?

Answer 17

-less ethical issues
-simpler, cheaper, easier to scale, more variable
-demonstrate multiple cell types and 3D architecture

Question 18

What are the disadvantages of using organoids to study pathogenesis?

Answer 18

-only mimics aspects of disease
-immortalised cell lines different to original tissue
-specialised growth conditions affect bact behaviour