Intro To Pathognesis

Question 1

3 types of pathogen

Answer 1

Primary
Secondary
Opportunistic

Question 2

What is a primary pathogen

Answer 2

Pathogen that is likely to cause infection if encounters naive host
“Once a pathogen always a pathogen”

Question 3

What is secondary pathogen

Answer 3

Need help to cause infection- More likely to cause disease once the ground has been
prepared for them by another pathogen

Question 4

What is an opportunistic pathogen

Answer 4

Pathogens that don’t normally cause infection but can if the host defences are compromised.

Question 5

Pathogenesis meaning

Answer 5

Processes/mechanisms of disease development
All things that bacteria/ host do that cause pathology

Question 6

Virulence meaning

Answer 6

Measure of capacity to damage/kill host
How harmful pathogen is

Question 7

Infectivity definition

Answer 7

How easy it is to catch disease
Reflects ability of organism to enter, colonise and survive in host (organism can have low virulence but high infectivity)

Question 8

Define Virulence factors

Answer 8

Component of bacteria that’s involved in pathogenesis, virulence or infectivity
-the molecules that assist the bacterium in colonizing the host at the cellular level

Question 9

Koch’s 4 postulates

Answer 9

-The organism or it’s products should be found in all individuals with the disease
-The organism should be isolated and be maintained in pure culture
-The pure culture inoculated into an individual should cause the disease
-The organism should be re-isolated in pure culture

Question 10

Do Koch’s postulates apply to all infectious disease?

Answer 10

No, as different types of pathogens exist e.g secondary pathogens which wont cause disease all the time

Question 11

What does multi factorial virulence mean?

Answer 11

Needs multiple virulence factors to cause disease (some bacteria wont work without correct combination of virulence factors)

Question 12

What is bacterial adhesion

Answer 12

process that allows bacteria to attach or adhere to other cells and surfaces. Adhesion is an important step for colonization of a new host or environment and can contribute to bacterial pathogenesis.

Question 13

2 types of colonisation life cycles

Answer 13

Intracellular vs extracellular

Question 14

Describe steps of extracellular pathogen lifecycle

Answer 14

1.Attachment
2.Resist phagocytosis
3.Resist action of complement
4.Acquire nutrients (iron/antibodies)

Question 15

Examples of extracellular life cycle pathogens

Answer 15

E.coli
A.pleuropneumoniae
B.anthracis
Clostridia sp.
S.aureus Streptococci sp.
Mycoplasma sp.

Question 16

Name steps of intracellular lifecycle colonisation

Answer 16

1. Attachment
2. Invasion
3. Resist intracellular destruction
4. Acquire nutrients

Question 17

Examples of intracellular pathogens

Answer 17

Mycobacteria sp.
L. monocytogenes
Salmonella sp.
Brucella sp.
Chlamydia sp.
Rickettsia sp.

Question 18

Defences against extracellular pathogens

Answer 18

Activation of the complement system, phagocytosis, and inflammatory response

Question 19

Common virulence factors of extracellular pathogens

Answer 19

• Adhesins
• Anti-phagocytic factors
– Capsules, surface proteins, toxins
• Anti-complement
– Inhibit: activation, deposition, function
– Many, diverse mechanisms
• Nutrient acquisition systems
– eg, iron uptakes systems

Question 20

What are capsules usually made of?

Answer 20

Acidic polysaccharides

Question 21

What are exotoxins and what do they do

Answer 21

A toxin secreted by bacteria
-cause damage to the host by destroying cells/ lyse RBC’s in vivo/ lyse phagocytes and affect their function

Question 22

What does mannheimia haemolytica leukotoxin do? (Exotoxin)

Answer 22

Act exclusively on leukocytes from ruminants
Damage to neutrophil leads to release of tissue destroying enzymes and attracts more neutrophils. Also affect platelets resulting in thrombosis

Question 23

What are DNAse secreted from pathogen used for

Answer 23

To escape NETs

Question 24

Which nutrient is essential to most bacteria for replication/infection?

Answer 24

Iron

Question 25

Many intracellular pathogens can survive in what cell type?

Answer 25

In macrophages

Question 26

Advantages of intracellular pathways surviving in macrophages

Answer 26

Long lived cell
Haven from extracellular defences of host
Rich supply of nutrients
Dissemination

Question 27

Survival strategies of intracellular bacteria in macrophages and which pathogen can do what strategy

Answer 27

Escape from the phagosome
L.monocytogenes, Rickettsia sp. Shigella sp.

Prevent acidification
M.tuberculosis, L.pneumophila

Prevent fusion
M.tuberculosis, Salmonella sp., Brucella sp.

Survival in phagolysosome
Coxiella Burnetti