Week 8 Microbes

Question 1

5 stages of infection

Answer 1

1. Incubation period
2. Prodromal Period (not all illness have this period)
3. Specific Illness Period
4. Decline
5. Convalescence

Question 2

5 Factors affecting incubation period

Answer 2

1. Microbial inoculum (dose)
2. Route of inoculation
3. Rate of replication of microbe
4. Host susceptibility
5. Host immune response

Question 3

What is latent infection?

Answer 3

After convalescence

Microorganism remains in patient’s body, when immune system of host declines -> maybe reactivation

Question 4

2 Types of microbes generally

Answer 4

1. Pathogens

2. Non-pathogens - do not cause disease

Question 5

2 Immunities

Answer 5

1. Innate immunity - at birth, no memory

2. Acquired immunity - organism-specific

Question 6

6 Basic steps of pathogenesis of infection

Answer 6

1. Encounter
2. Entry
3. Spread - local and beyond
4. Multiplication
5. Damage
6. Outcome

Question 7

What is virulence factor?

Answer 7

Micorbial factors that enhance the organism’s ability to colonize, invade and multiply inside host

Question 8

The chain of infection

Answer 8

1. Infectious agent
2. Reservoir
3. Exit Portal
4. Transmission
5. Entry Portals
6. Susceptible Host

Question 9

Major routes of transmission

Answer 9

1. Inhalation
2. Ingestion
3. Contact - direct/indirect
4. Bites/cuts/wounds
5. Iatrogenic - involves blood transfusion/transplantation

Question 10

3 Types of bacteria according to staining properties

Answer 10

1. Gram-positive bacteria (violet/dark blue)
2. Gram-negative bacteria (red/pink)
3. Cell wall-deficient bacteria

Question 11

Common diseases caused by Gram-negative bacteria

Answer 11

1. Urinary tract infection
2. GI tract infection
3. Sexually-transmitted diseases
4. Zoonoses

Question 12

4 types of bacteria morphologically

Answer 12

1. Cocci - spherical
2. Bacilli - rod-shaped
3. Spirochaetes - curved
4. Cell wall-deficient

Question 13

Important component of bacterial cell wall

only present in bacteria

Answer 13

Peptidoglycan

Function: give structural integrity in bacterial cell

Question 14

Difference between Gram-positive and Gram-negative bacterial cell wall

Answer 14

Gram-positive bacteria: thick peptidoglycan layer

Gram-negative bacteria: thin peptidoglycan layer -> lipid outer membrane (less permeable to antibiotics)

Question 15

4 types of bacteria according to oxygen requirement

Answer 15

1. Strictly aerobic
2. Facultatively anaerobic
3. Microaerophilic
4. Strictly anaerobic

Question 16

4 Pathogenic mechanisms of bacteria

Answer 16

1. Invasion
2. Toxin
3. Immunopathology
4. Oncogenesis

Question 17

6 Infectious agents

Answer 17

1. Helminths
2. Protozoa
3. Fungi
4. Bacteria
5. Virus
6. Prion

Question 18

5 Mechanisms of action of antibacterial agents

Answer 18

1. Peptidoglycan Synthesis
2. Protein Synthesis
3. Nucleic acid Synthesis
4. Folate Synthesis
5. Cell membrane integrity

Question 19

What is viraemia?

Answer 19

Presence of virus in blood

Question 20

Virus replication cycle

Answer 20

1. Attachment
2. Penetration
3. Uncoating
4. Viral protein synthesis
5. Viral nucleic acid replication
6. Virus assembly
7. Viral release

Question 21

3 Pathogenic mechanisms of virus

Answer 21

1. Cytolysis
2. Immunopathology
3. Oncogenesis - induction of tumours

Question 22

2 General ways of viral diagnosis

Answer 22

1. Detect the virus

2. Detect the host antibody response

Question 23

What is prion?

Answer 23

Infectious protein

Question 24

Medically important groups of parasites

Answer 24

1. Protozoa
2. Helminths: nematodes, trematodes, cestodes
3. Arthropods

Question 25

Life cycle of parasites

Answer 25

1. Agent: parasite itself 2. Vector: for transmission 3. Intermediate host: harbours asexual stage Definitive host: harbours sexual stage (mature)

Question 26

Microorganism causing malaria

Answer 26

Protozoa: Plasmodium spp. (genus)

Question 27

What are relapse and recrudescence?

Answer 27

Relapse: recurrence of symptoms after complete initial clearing of parasitaemia Recrudescence: recurrence of symptoms after initial parasitaemia is reduced to a very low level (not completely cleared)

Question 28

Vector for natural transmission of malaria

Answer 28

Female Anopheles mosquitoes