MIP: Introduction to Microbiology and Infectious Disease

Question 1

What are Koch’s Postulates? What are their limitations?

Answer 1

1) The microbe must be associated with lesions of the disease and not found in the healthy (Some pathogens can be found in healthy individuals) 2) Microbe must be isolated from the lesions of the disease and grown in pure culture (not all bacteria can be grown in a petri dish) 3) A pure culture should cause disease if inoculated into a susceptible host (suitable animal models not always available; not all infected will develop disease) 4) Microbe must be re-isolated 5) Effective chemotherapy should eradicate the microbe and cure disease (doesn’t address molecular mimicry)

Question 2

What is the current ‘definition’ of infection?

Answer 2

Acquisition of a microbe with several possible outcomes

Question 3

What is a pathogen?

Answer 3

A microbe capable of causing host damage, often through elaboration of virulence factors

Question 4

What is a commensal?

Answer 4

A microbe that induces either no damage or clinically unapparent damage after primary infection

Question 5

In which condition is S. mutans pathogenic and what are the outcomes?

Answer 5

With high sucrose content, S. mutans can turn sucrose into acids and cause cavities

Question 6

True or False: Small bronchi and alveoli are normally sterile?

Answer 6

True

Question 7

What is virulence?

Answer 7

The relative capacity of a microbe to cause damage

Question 8

True or False: Virulence is solely a microbial trait

Answer 8

False

Question 9

What makes a microbe virulent?

Answer 9

Capacity to overcome host defenses, severity of disease, LD50, invasiveness of microbe in host, infectivity or damage induced in host, capacity to grow and multiply in host

Question 10

What is a virulence factor?

Answer 10

A microbial characteristic that allows a microorganism to cause disease

Question 11

What are the 5 classes of virulence factors and the function of each?

Answer 11

Adhesins- mediate adhesion of microbe to host; invasins- promote the uptake of bacteria into cells that are not normally phagocytic; Impedins- prevent normal functioning of the host immune response without damaging host; aggresins- directly damage host tissue or actively promote spread of a pathogen; modulins- affect host immune response often to the detriment of the host

Question 12

What class of virulence factor are exotoxins?

Answer 12

Aggresssins

Question 13

What class of virulence factor are super-antigens?

Answer 13

Modulins

Question 14

What class of virulence factor is LPS?

Answer 14

Modulin