Chapter 16: Host-Microbe Interactions: Duration + Distribution of pathogens

Question 1

What are the 3 durations of symptoms?

Answer 1

• acute
• chronic
• latent

Question 2

What is an acute symptom? (2)

Answer 2

• Rapidly developing
• short duration
  ex. influenza

Question 3

What is a chronic symptom? (2)

Answer 3

• slow to develop
• continual duration
  ex. tuberculosis

Question 4

What is a latent symptom? (2)

Answer 4

• inactive for a period of time
• can be reactivated
• ex. cold sores - herpes virus

Question 5

Why is the number of microbes important?

Answer 5

• if too few microbes enter, immune system will fight them off and prevent disease

Question 6

How will the likelihood of disease increase?

Answer 6

microbe number increases

Question 7

How can virulence and pathogenicity of a microbe be expressed numerically? (2)

Answer 7

• infectious dose
• Potency of a toxin

Question 8

Infectious dose: what does ID50 mean?

Answer 8

• causes infection in 50% of the population
  ex. Bacillus anthracis

Question 9

How many endospores does ID50 equate to, by:
- ingestion
- inhalation
- through a cute in the skin

Answer 9

ingestion: 250 000 to 1 mil
inhalation: 10 000 to 20 000
Through a cut in the skin: 10-20

Question 10

How is potency of a toxin expressed by? (2)

Answer 10

• lethal dose
• LD50 kills 50% of the infected population

Question 11

What is a localized infection?

Answer 11

• confined to small area of the body

Question 12

What is a systemic infection?

Answer 12

• microbes or toxins are spread throughout the body
  ex. covid

Question 13

What is septicimia?

Answer 13

• systemic infection of the blood

Question 14

What are 3 types of septicimia?

Answer 14

bacteremia - bacteria in the blood
toxemia - toxins in the blood
viremia - viruses in the blood

Question 15

What is sepsis?

Answer 15

• life threatening systemic inflammatory response, usually due to bacteremia

Question 16

How is Clostridium Tetani an example of toxemia?

Answer 16

• causes infection of a cut
• releases toxins in the blood