Host Microbe Interactions

Question 1

True or false: Infection of a host always causes disease or harm.

Answer 1

False. It may or may not negatively affect the host

Question 2

What is an infectious disease?

Answer 2

○ Definition: A disease caused by an infection with a microbe.
§ Some are communicable = transmitted patient to patient
§ Non-communicable = not transmitted patient to patient

Question 3

What is pathogenicity? What is the difference between a Frank and Opportunistic Pathogen?

Answer 3

Definition: The ability of something (usually a microbial species) to cause disease.

Opportunistic pathogens cause disease in compromised hosts. Frank Pathogen cause disease in normal hosts.

Question 4

What is the relationship between virulence and microbes required for disease?

Answer 4

High Virulence= low amount of bacteria required for disease.

Question 5

How can we show that a microbe causes a certain disease?

Answer 5

a. Specific microbes are present in characteristic lesions of the disease
b. The specific microbes can be isolated and grown in vitro.
c. Injection of the cultured microbes into animals reproduces the disease that you see in humans
d. The specific microbes can be re-isolated from lesions of the disease in animals.

This process is known as Koch’s Postulates

Question 6

What are some of the limitations of Koch’s Postulates?

Answer 6

1. Some inf. diseases don’t have “characteristic lesions”
2. Some microbes may die in vitro
3. Only looks at the microbe and not the host (ie doesn’t determine what makes a good host)

Question 7

What are the stages of pathogenesis of an infectious disease?

Answer 7

Think about it logically, the progression of the disease goes:

1. Encounter
2. Entry
3. Spread
4. Multiplication of microbe
5. Damage
6. Outcome: does host or microbe win?

Question 8

Stage: Entry

In order to colonize in a host, a microbe must have good ___________ (action) to host tissue.

Answer 8

Adherence

Question 9

Stage: Spread

What are some factors that promote spreading in a host?
What inhibits spreading?

Answer 9

Promote: Hyaluronidase, elastase, collagenase. They all break down ECM.

Inihibit: Coagulase inhibits spread of microbes because it lays down fibrin to “wall off” and localize infection.

Question 10

Stage: Multiplication

In order for a microbe to stay in a host, the rate of clearance must be _____________ than the rate of replication.

Answer 10

Less than

Replication rate > clearance rate in order to remain in host

Ask yourself: Why do some microbes grow faster in vitro than in vivo?
*Host immunity

Question 11

Which type of immunity defends against future recurrences of a disease?

Answer 11

Acquired Immunity

Question 12

On which body surface is staphylococci most present?

Answer 12

Skin

Question 13

On which body surface are Neisseria bacteria most present?

Answer 13

Oropharynx

Question 14

What are some factors that affect your microbiome?

Answer 14

1. Diet
2. Antibiotic use
3. Anatomy
4. Genetics

Question 15

Why is your microbiome important?

Answer 15

1. Effects tissue Differentiation
2. Produces Vitamins
3. Biochemical conversions (bilirubin degradation, drug metabolism, production of carcinogens)
4. Competition with pathogens for colonization of surfaces (if there’s no space to land, pathogens can’t colonize and survive)

Question 16

What is the paradigm for how does Cholera infects the body?

Answer 16

Alters function of small intestine but not structure

Question 17

What is the paradigm for how does Pneumococcal pneumonia infects the body?

Answer 17

Acute Inflammatory disease caused by bacteria that grows extracellularly

Question 18

What is the paradigm for how does tuburculosis infects the body?

Answer 18

Chronic disease caused by facultative intracellular bacterium and controlled by cell-mediated immunity.

Question 19

What is the paradigm for Rheumatic Fever?

Answer 19

Follows infection;

A disease resulting from poorly treated Strep Throat or Scarlet fever (streptococcal infection).