Bacterial Pathogenesis

Question 1

What is pathogenesis?

Answer 1

How a disease begins or develops

Question 2

Why does pathogenesis occur?

Answer 2

It occurs as a consequence of complex interactions between an infecting pathogen and the host immune system

Question 3

What is pathogenicity?

Answer 3

The ability of a pathogenic agent to cause disease

Question 4

Who were the postulates formulated by and when?

Answer 4

Robert Koch & Friedrich Loafer in 1884

Question 5

How is the pathogen capable of causing disease?

Answer 5

Point of entry
Evasion & Survival
Adherence & attachment
Colonisation at the site of adherence
Disease symptoms caused by bacterial toxins or invasion

Question 6

What are the entry portals for a pathogen?

Answer 6

Respiratory
Skin
GIT
Genital

Question 7

What are examples of pathogens that enter through the respiratory system?

Answer 7

Mycobacterium tuberculosis
Streptococcus pneumoniae
Haemophilus influenza

Question 8

What is an example of pathogen that enters through the skin?

Answer 8

Clostridium tetani

Question 9

Where do these pathogens enter the organism from?
Salmonella
Vibrio Cholera
Shigella dysenteriae

Answer 9

GIT

Question 10

Which pathogen enters through the genitals?

Answer 10

Neisseria gonorrhoeae

Question 11

Are entry portals specific or not?

Answer 11

Yes, the pathogen needs to enter through the specific portal in order to cause the disease otherwise there is no disease

Question 12

Which processes help the pathogen to evade and survive?

Answer 12

Inhibition of phagocytosis
Modulation of surface structure to avoid recognition
Secretion of toxins that modulate the cell death pathways which causes apoptosis

Question 13

What are the ways in which pathogens modulate their surface to avoid recognition?

Answer 13

Complement inhibition
Antigenic variability

Question 14

Which staphylococcus-related protein decreases phagocytosis?

Answer 14

Staphylococcus aureus Protein A

Question 15

How does SpA decrease phagocytosis?

Answer 15

It can affect the antibodies specifically or the source (B-cells) themselves

Question 16

How does SpA affect antibodies?

Answer 16

Attache to antibodies,
Antibodies cannot perform their action
Antibody sequestered
Decreased phagocytosis

Question 17

How does SpA affect the source?

Answer 17

Attaches to B cells
It acts as a superantigen toxin
Binds to the B cells through certain binding domains
It causes B-cell apoptosis
No adapted immune response
Decreased phagocytosis

Question 18

What does factor H do?

Answer 18

Tessera meningitidis factor H binding protein evades complement-mediated phagocytosis

Question 19

How does factor H work?

Answer 19

fHBP scavenges Factor H, which inactivates C3b

Question 20

What is the effect of Factor H?

Answer 20

Minimizing complement activation and enhancing the survival of pathogen

Question 21

What are the different bacterial adherence factors?

Answer 21

Adhesin
Capsule
Lipopolysaccharides (LPS) Technoic acids and lipoteichoic acids (LTA)
Fimbriae
Pilli

Question 22

What is colonisation?

Answer 22

Establishment and growth of a microorganism on body surface

Question 23

What are the stages of colonisation?

Answer 23

1. Enter lumen of new host, pass through mucus
2. Bind epithelial surface via host surface carbohydrates and protein
3. Obtain nutrients from host
4. Evade host cellular and humoral immunity
5. Exploit inflammation to exit or invade host

Question 24

What is virulence?

Answer 24

The degree of pathogenicity of a particular organism and the extent of damage that an organism cause to the host

Question 25

How is bacterial virulence measured?

Answer 25

By calculating the number of bacteria required to cause the disease

Question 26

On a graph which line would have the higher virulence?

Answer 26

The one that reached 50% of animals infected faster

Question 27

What is infective dose 50?

Answer 27

The number of bacteria needed to infect 50% of the animals (host) exposed to them

Question 28

What is lethal dose 50?

Answer 28

The number of bacteria needed to kill 50% of the animals (host) exposed to them