M1 Nature of Infectious Disease

Question 1

Explain the term virulence

Answer 1

the capacity of a microbe to cause damage to the host

Question 2

Explain the term parasitic

Answer 2

live on or in living creatures causing harm/damage to the host

Question 3

Explain the term commensal

Answer 3

organism gains advantage but host does not gain from association

Question 4

Explain the term mutualistic

Answer 4

relationship beneficial for both

Question 5

Explain the term endogenous infection. Give an example

Answer 5

bacteria/fungi part of host’s natural microbiome; 2 things may happen for infection to occur

Question 6

Explain the term exogenous infection

Answer 6

infective material derived from outside patient’s body

Question 7

Explain the term virulence factor

Answer 7

component of a pathogen that contributes to its ability to cause disease

Question 8

Explain the term epidemiology

Answer 8

the study of the occurrence, spread and control of disease

Question 9

What is the significance of Koch’s postulates?

Answer 9

critically important for establishing the criteria for microorganisms causing disease

Question 10

How have koch’s postulates been adapted?

Answer 10

to include molecular mechanisms deployed by pathogen and host

Question 11

What are the points on the cycle of infection?

Answer 11

pathogen
reservoir
portal of exit
means of transmission
portal of entry
new host

Question 12

How can the cycle of infection vary depending on the reservoir?

Answer 12

patient, patient surroundings, equipment etc (inanimate/animate)

Question 13

How can the cycle of infection vary depending on the method of transmission?

Answer 13

natural/artificial, direct/indirect, air-borne, vector spread

Question 14

What did Koch discover in the 1880s ?

Answer 14

Germ theory of Disease

Question 15

Explain the term pathogen

Answer 15

a harmful organism that produces a pathology

Question 16

Explain the term opportunistic pathogen, give an example

Answer 16

an organism that cause infection when opportunity/change in natural immunity arises, e.g. in an immunocompromised individual

Question 17

Explain the term LD50

Answer 17

lethal dose required to kill 50% of hosts

Question 18

Explain the term ID50

Answer 18

infectious dose necessary to infect 50% of hosts

Question 19

Explain the a symbiotic/mutualistic relationship

Answer 19

beneficial for both, organism can produce nutrients or vitamins, can degrade harmful chemicals, can exclude access.colonisation by exogenous pathogens

Question 20

Explain the term microbiome

Answer 20

community, or its associated genetic material, associated with host during health or disease

Question 21

What family of bacteria is the oral cavity dominated by?

Answer 21

Streptococci

Question 22

Give an example of 2 virulence factors

Answer 22

• adhesin = enable binding of the organism to the host

- impedin = enable the organism to avoid the host defence mechanisms

Question 23

What are the 4 types of occurrence in epidemiology?

Answer 23

sporadic, endemic, epidemic, pandemic

Question 24

Explain the term dynamic relationship

Answer 24

endogenous bacteria can include species that can shift between lifestyles and become parasites.

Question 25

give 2 ways in which endogenous infection can occur

Answer 25

bacteria/fungi has become displaced/transfer from non-sterile to normally sterile site. e.g. S. sanguinis mouth to blood to heart = endocarditis

OR

Change in natural flora due to antibiotic therapy