L39: Host Microbe Relationship And Microbial Pathogenesis

Question 1

Incubation period

Answer 1

Time elapsed between exposure and symptom appearance

Question 2

Latent infection

Answer 2

• Pathogens are not actively dividing (dormant)
• still viable and infectious / transmitted
• clearance is not complete, no apparent symptoms
• can be reactivated

Question 3

Chronic infection

Answer 3

Low level replication vs clearance

—> still cause tissue damage

Question 4

Slow chronic infection

Answer 4

Subacute problem but levels of infectious virus slowly increasing
E.g. measles virus —> subacute sclerosing panencephalitis

Question 5

Characteristics of virulent pathogen

Answer 5

1. Low infective dose
2. High attack rate
3. Number and potency of virulence factors: colonise, proliferate, invade, modify
4. High morbidity and mortality

Question 6

6 steps of pathogenesis

Answer 6

1. Encounter: exogenous / endogenous (normal flora)
2. Entry: inhalation / ingestion / bites / contact / transplant
3. Spread: local (symptoms may be systemic due to cytokines)/ systemic (lymphatic, bloodstream, nerve) —> cell/organ trophism
4. Multiplication
5. Damage
6. Outcome: invade vs defend, inoculum size, mode of inoculation, medical treatment

Question 7

Endotoxin-mediated disease

Answer 7

1. Cholera
2. Diphtheria
3. Tetanus