Week 2: Host-microbe interactions

Question 1

Describe a Prion

Answer 1

Non-living, protein only

Question 2

Describe a eukaryotic infectious agent

Answer 2

Living, membrane-bound organelles

Question 3

Describe bacteria

Answer 3

Living, single-celled

Question 4

Describe a virus

Answer 4

Non-living, obligate intracellular parasite

Question 5

What features create a susceptible host?

Answer 5

Age, nutrition, illness, immunosuppression, genetics, anatomical defects

Question 6

How does age make you a susceptible host?

Answer 6

The very young have immature Immune systems
The elderly have an ageing immune system

The extremities of age result in an impaired ability to mount an effective immune response

Question 7

How does nutrition create a susceptible host

Answer 7

Inadequate levels of protein and micronutrients including vitamins A,B,C, D and E; as well as minerals iron, selenium and zinc
All leading to impaired immune function and delayed wound healing

Question 8

How can illness create a susceptible host

Answer 8

Co-morbid conditions lead to increased host susceptibility due to disruption of physiological functions

Question 9

How does immunosuppression create a susceptible host

Answer 9

Innate or acquired, resulting suppression of the innate and/or adaptive immune response. (Chemotherapy)

Question 10

How do genetics affect host susceptibility

Answer 10

Heritable traits result in altered phenotypes can increase risk.
Some genetic mutations lead to changes in physiological functions associated with innate immune response
Some mutations result in disrupted or delayed recognition of infectious agents

Question 11

How do anatomical defects create a susceptible host

Answer 11

Changes in normal physiological functions of organs or organ systems

Question 12

What are the three basic elements required for transmission of infectious agents

Answer 12

Source of infectious agents
Susceptible host
Mode of transmission

Question 13

How does horizontal transmission occur

Answer 13

Between individuals via direct contact or indirectly by contact with the reservoir or vehicle or vector.

Question 14

What is contact transmission

Answer 14

Direct transferral between one host and another

Question 15

Direct contact transmission

Answer 15

Transmission occurs when susceptible hosts come into contact with the skin or bodily secretions of an infected person

Question 16

Indirect contact transmission

Answer 16

When susceptible host touches an inanimate object

Question 17

What are the major portals of entry and exit of a human host

Answer 17

Natural openings related to physiological function

Breaches of barrier integrity

Question 18

How does the skin protect against infectious agents

Answer 18

Physical barrier to protect against pathogens

Question 19

How do mucous membranes protect against infectious agents

Answer 19

Physical barrier against pathogen entry from superficial openings to deeper tissues

Question 20

What are the naturally existing portals of entry in the body

Answer 20

Skin, respiratory tract, gastrointestinal tract, urine ital tract, congenital infections

Question 21

How is skin a portal of entry

Answer 21

Cracks or injury to the skin create portals of entry. Some agents can however burrow through intact skin.

Question 22

How do infectious agents enter the respiratory tract

Answer 22

Via inhalation or aerosols, spores and particular matter

Question 23

How do infectious agents enter the gastrointestinal tract

Answer 23

Contaminated food or drink

Question 24

How do infectious agents infect the urogenital tract

Answer 24

Infectious agents can ascend the urinary tract

Sexually transmissible pathogens are inoculated directly during bodily contact

Question 25

What are the naturally existing portals of exit

Answer 25

Skin, respiratory tract, gastrointestinal tract, urogenital tract, blood

Question 26

How is skin a portal of exit

Answer 26

Superficial layers of skin shed leading to direct and indirect transmission

Question 27

How is the respiratory tract a natural portal of exit

Answer 27

Infectious agents present in mucosal secretions including saliva, mucous and sputum.
Excreted by sneezing or coughing and talking

Question 28

How is the gastrointestinal tract a portal of exit

Answer 28

Infectious agents cause irritation of interstitial mucosa. The shedding of large volumes of the agents in frequent or water stool.

Question 29

How is the urogenital tract a portal of exit

Answer 29

Infectious agents causing sexually transmittable infections are shed in high numbers in seminal fluid or vaginal secretions

Question 30

How is blood a portal of exit

Answer 30

Infections being transmitted haematogenously to distant body sites and to unborn babies

Question 31

What is the definition of common vehicle transmission

Answer 31

Agents transmitted by a common inanimate vehicle, with multiple cases resulting from exposure

Question 32

What is contact transmission

Answer 32

An infection spread via direct or indirect contact with an infected person

Question 33

Immunocompromised

Answer 33

Having an impaired immune system making a person more susceptible to infectious agents

Question 34

Source

Answer 34

The origin of an infectious agent