Pathogenesis

Question 1

Koch’s Postulates

Answer 1

1. The suspected agent must be present in every case of the disease
2. The agent must be isolated and grown in culture
3. The cultured agent must cause disease when inoculated into a healthy individual
4. The same agent must be re-isolated from this new host

Question 2

Problems with Koch’s Postulates

Answer 2

Not all pathogens can be cultured in the lab.

Diseases are sometimes caused by a combination of pathogens.

Question 3

Extracellular enzymes

Answer 3

Secreted by the pathogens to catalyse reactions in the host, including dissolving structures in the body.

Question 4

Toxins

Answer 4

Chemicals that harm tissues or trigger an immune response which causes damage.

Question 5

What is toxemia?

Answer 5

Where toxins spread in the bloodstream past the site of infection

Question 6

What is an endotoxin?

Answer 6

A toxin released by gram negative bacteria upon death which enters the blood causing coagulation

Question 7

What is an exotoxin?

Answer 7

A toxin released from bacteria to destroy host cells

Question 8

Antiphagocytic factors include prevent phagocytosis occurring in the host. These factors include…

Answer 8

Chemicals prevent fusion of lysosome to phagocyte.

Leucocidins destroy phagocytes.

Viral capsules are sometimes recognised as non-foreign, so are released.

Question 9

Adhesion

Answer 9

Process where microorganisms adhere to cells, allowing them to replicate. Attachment proteins help with this.

Question 10

Biofilms

Answer 10

Complex relationships between different microorganisms where an extracellular matrix is developed, allowing cells to adhere to one another. This is for protection and sharing nutrients.

Question 11

Define pathogenicity

Answer 11

The ability of an organism to cause disease in a host