lec 3-4

Question 1

infection def.

Answer 1

when pathogens or microbes invade host and start to multiply

Question 2

disease def.

Answer 2

when normal tissue function is impaired as a result of pathogen invasion and growth

Question 3

3 types of disease

Answer 3

genetic
ageing
infectious

Question 4

genetic disease

Answer 4

due to a specific genotype

e.g. cystic fibrosis

Question 5

ageing disease

Answer 5

occurs later in life

e.g. atherosclerosis

Question 6

infectious disease

Answer 6

individual contracts outside agent

e.g. measles

Question 7

pathogen def.

Answer 7

organism capable of causing disease in a susceptible host

Question 8

true pathogen

Answer 8

infectious agent that causes disease in virtually any susceptible host

Question 9

opportunistic pathogen

Answer 9

potentially infectious agents that rarely cause disease in individuals with healthy immune systems

Question 10

pathogenicity def.

Answer 10

capacity of a microbe to cause disease in a susceptible host

Question 11

what kind of variable is pathogenicity

Answer 11

discontinuous

microbial variable that can only be expressed in a susceptible host

Question 12

4 interactions between microbes and hosts

Answer 12

commensalism
colonisation
latency
disease

Question 13

commensalism

Answer 13

interaction between microbe and host - one benefits and one is not affected

Question 14

colonisation

Answer 14

microbes living in or on your body but do not make you sick

Question 15

latency

Answer 15

ability of microbes to lie dormant e.g. HPV, TB, HIV

Question 16

host variables that affect the outcome of host-microbe interactions

Answer 16

age
stress
state of immune system
genetics
environment

Question 17

virulence def.

Answer 17

amount of disease or damage that is caused

Question 18

what type of variable is virulence?

Answer 18

continuous

Question 19

ways to measure virulence

Answer 19

median infective dose

median lethal dose

Question 20

median infective dose (ID50)

Answer 20

amount of pathogenic microorganisms that produce demonstrable infection in 50% of the test subjects

Question 21

median lethal dose (LD50)

Answer 21

quantity of an agent that will kill 50% of the test subjects

e.g. amount of radiation required to kill half population in a given time

Question 22

unit LD50

Answer 22

number of cells

Question 23

factors affceting LD50 and ID50

Answer 23

host
immunological status
physiological status
genetic makeup
route of infection - inhalation, cutaneous

Question 24

3 types of virulence factors

Answer 24

toxins
surface coats that inhibit phagocytosis
surface receptors that bind to host cells

Question 25

planktonic bacteria

Answer 25

microbes are floating in aqueous/liquid phase

Question 26

biofilm

Answer 26

formed by adherence of microbes to a surface

they are well protected due to physical nature of biofilm

Question 27

communication in biofilm infections

Answer 27

cell-cell signalling
quorum sensing
social organisation/interconnections

Question 28

geobacteria

Answer 28

microbes form networks - electric signalling

Question 29

epidemiology

Answer 29

effects of pathogens on populations
where and when diseases occur
incidence and prevalence

Question 30

incidence

Answer 30

number of new cases of a disease in a given population

frequency of a disease

Question 31

prevalence

Answer 31

total number of both new and existing cases of disease

Question 32

exogenous

Answer 32

something we get from outside the body

e.g. clostridium spp.

Question 33

endogenous

Answer 33

internal cause or origin

e.g. staphylococcus

Question 34

dysbiosis

Answer 34

microbial imbalance or maladaptation on or inside the body

Question 35

how can you get a HAI

Answer 35

hospital acquired infection

• intravenous canule
• surgery
• skin infection
• urinary catheter
• gastrointestinal infection

Question 36

gram -ve pathogens

Answer 36

asymmetrical outer phospholipid bilayer
lipopolysccharide
big outer membrane

Question 37

serogroup

Answer 37

a group of bacteria containing a common antigen

different carbohydrates - different serogroups

Question 38

capsule

Answer 38

carbohydrate slime layer

protects proteins/surface components against phagocytosis

Question 39

antigenic variation

Answer 39

turning on and off capsule production

Question 40

gram +ve pathogens

Answer 40

easy to produce vaccines against them
thick peptidoglycan layer

disease caused by spread of the toxin- classical virulence factor