PATHOGENESIS - Bacteria

Question 1

What is a primary pathogen?

Answer 1

A primary pathogen is a pathogen that can cause disease in a host regardless of the host natural biota and immune system

Question 2

What is a secondary pathogen?

Answer 2

A secondary pathogen is a pathogen that causes disease following a first infection

Question 3

What is an opportunistic pathogen?

Answer 3

An opportunistic pathogen is a pathogen that causes disease when the host defences are compromised

Question 4

What is virulence?

Answer 4

Virulence is a measure of a pathogens ability to cause harm and/or kill the host

Question 5

What is infectivity?

Answer 5

Infectivity is the ability of a pathogen to enter, colonise and survive within a host

Question 6

What are virulence factors?

Answer 6

Virulence factors are components of a pathogen involved in pathogenesis, virulence and infectivity

Question 7

‘Virulence is multifactorial’. What does this statement mean?

Answer 7

Pathogens require multiple virulence factors to cause disease

Question 8

Why is the study of virulence factors so important?

Answer 8

Studying virulence factors is important for making vaccinations

Question 9

What technique can be used to study virulence factors in the lab?

Answer 9

Site directed mutagenesis

Question 10

What is the purpose of Koch’s postulates?

Answer 10

Koch’s postulates are guidelines for establishing which microbes cause specific diseases

Question 11

What are two anti-phagocytic factors used by extracellular bacteria to evade the host immune system?

Answer 11

Capsules
Exotoxins

Question 12

Give an example of an exotoxin secreted by bacteria to evade phagocytosis?

Answer 12

Manhaemia haemolytic leukotoxin

Question 13

What is secreted by pathogenic Staphylococcus and Streptococcus to escape neutrophil extracellular traps (NETs)?

Answer 13

Pathogenic Staphylococcus and Streptococcus secrete DNAse to escape neutrophil extracellular traps (NETs)

Question 14

What is the function of siderophores?

Answer 14

Siderophores are low molecular weight, high affinity iron collators that bacteria synthesise in low iron environments. These collators are so high affinity that they can strip iron from the host iron binding proteins (transferrin and lactoferrin) using a ferric siderophore receptor

Question 15

List two species of bacteria that use siderophores

Answer 15

E. coli
Salmonella

Question 16

What is the function of transferrin/lactoferrin binding proteins?

Answer 16

Transferrin/lactoferrin binding proteins are synthesised by bacteria within low iron environments to bind to iron on host iron binding proteins (transferrin and lactoferrin)

Question 17

(T/F) Both siderophores and transferrin/lactoferrin binding proteins are host independent

Answer 17

FALSE. Only siderophores are host independent, transferrin/lactoferrin binding proteins are host specific

Question 18

How do most intracellular bacteria that have evolved to live within macrophages evade the immune response?

Answer 18

These intracellular bacteria inhibit phagolysosome fusion within the macrophage

Question 19

What is the only known bacteria that can survive within phagolysosomes?

Answer 19

Coxiella burnetii

Question 20

Give two examples of bacteria and their exotoxins which produce very specific clinical signs

Answer 20

Clostridium tetani producing tetanus toxin
Staphylococcus producing exfoliative toxin