lecture 3) concept of virulence and infectivity

Question 1

define what is meant by the term disease

Answer 1

growth of pathogens that impairs tissue function

Question 2

give an example of a disease in plants

Answer 2

rice blast fungus

Question 3

what does the rice blast fungus do and what is it’s impact?

Answer 3

it is a plant disease that kills one of the most important food sources in the world
more rice means more people can eat which has an impact on the price of rice

Question 4

name 3 different types of disease

Answer 4

genetic (aka metabolic)
disease of ageing
infectious disease

Question 5

describe and given an example of a genetic disease

Answer 5

eg. cystic fibrosis

those with CF have a specific genotype due to impaired transport of Cl- across the cell membrane

Question 6

describe and give an example of disease of ageing

Answer 6

eg. atherosclerosis
build up of plaque/cholesterol over a period of time
the older you are the more plaque will have built up in your arteries therefore based on age

Question 7

describe and give an example of an infectious disease

Answer 7

eg measles

individual contracts outside agent

Question 8

describe the MMR vaccine debate

Answer 8

we are close to eradicating the disease in the UK
people feared taking the vaccine would do you more harm than good
people stopped taking the vaccine
lead to measles outbreaks

Question 9

define the term infection

Answer 9

a pathogen invades the host and begins growing in the host

Question 10

what is a latent infection?

Answer 10

when a pathogen invades a host but doesnt cause disease

a disease is only caused when there is tissue impairment

Question 11

give examples of latent infections

Answer 11

herpes, HIV, TB

Question 12

name 3 possible ways infections can spread

Answer 12

skin to skin contact (mites)
body fluids (HIV)
water droplets (legionella)

Question 13

why is legionella so dangerous?

Answer 13

can be fatal as it is latent in the environment but can cause disease once inside the host

Question 14

define the term pathogen

Answer 14

an organism that is capable of causing disease in a susceptible host

Question 15

what is characteristic of the pathogens in normal microbiota?

Answer 15

they dont cause disease

Question 16

what is a true pathogen?

Answer 16

an infectious agent that causes disease in virtually any susceptible host

Question 17

what is an opportunistic pathogen?

Answer 17

potentially infectious agents that cause disease in individuals with healthy immune systems
eg candida; may cause disease in those who are immunocompromised, when in the presence of MRSE - v toxic

Question 18

define the term pathogenicity

Answer 18

the capacity of the microbe to cause disease

Question 19

what are some of the characteristics of pathogenicity?

Answer 19

microbial variable
discontinuous variable - either is or isnt pathogenic
only expressed in susceptible host therefore dependent on host variables

Question 20

list 4 host variables

Answer 20

age
diet
stress
status of immune system

Question 21

define the term virulence

Answer 21

amount of damage or disease that can be caused to the host

Question 22

how would you measure virulence?

Answer 22

the unit is cells kills/those that caused disease

Question 23

what does ID50 stand for?

Answer 23

the median infective dose

the amount of microorganism that will produce demonstratable infection in 50% of it test subjects

Question 24

what does LD50 stand for?

Answer 24

quantity of agent needed to kill 50% of test subjects

Question 25

are ID50s and LD50s the same for every microorganism?

Answer 25

no, ID50s and LD50s vary for each microorganism as some are more virulent than others eg TB vs C. diff

Question 26

name 3 influences of virulence

Answer 26

immunological status physiological status route of infection

Question 27

name 3 routes of infection

Answer 27

ingestion skin inhalation

Question 28

name 3 host influences on virulence

Answer 28

age genetics stress

Question 29

using an example, explain how the route of infection can determine the virulence of a pathogen

Answer 29

anthrax cutaneous; found on the skin, causes sores, can be treated inhaled; same number of spores inhaled as on the skin can kill you. inhaled anthrax has a lower ID50

Question 30

what is the impact of climate change on disease?

Answer 30

new climate = new diseases = new plant diseases = migration

Question 31

what is a virulence factor?

Answer 31

describes a microbial characteristic caused by specific genes intrinsic factor outcomes dependent on host

Question 32

what is the first of koch's molecular postulates?

Answer 32

the gene under investigation should be found in all pathogenic strains of a species but absent from non-pathogenic strains

Question 33

what is the 2nd of koch's molecular postulates?

Answer 33

the gene causing the virulence but be expressed during infection

Question 34

what is the 3rd kochs molecular postulates?

Answer 34

inactivation of the gene causing virulence must lead to measurable loss of virulence this loss must be less in microorganisms with unaltered gene

Question 35

what is the 4th kochs molecular postulate?

Answer 35

reversion or allelic replacement of mutated gene should restore pathogenicity

Question 36

how would you monitor gene expression using RNA sequencing?

Answer 36

sequence of the gene known primer made to stick to product using 16S rRNA method measure light emitted from the number of copies from a gene

Question 37

what is the copy number in PCR?

Answer 37

how many pieces of RNA is expressed at a certain time

Question 38

what is a limitation of the virulence factor concept?

Answer 38

hard to apply to microbes whose pathogenicity is limited (immunocompromised)

Question 39

what is meant by the term planktonic when describing bacterial state?

Answer 39

bacteria are in the aqueous phase | not stuck on a surface

Question 40

what is meant by the term biofilm?

Answer 40

bacteria are attached to a surface

Question 41

what is characteristic about the genetics between biofilms and planktonic bacteria?

Answer 41

they have different gene expression as they know if they are on a surface or not

Question 42

what is more susceptible to antibiotics; planktonic or biofilm bacteria? why?

Answer 42

planktonic more susceptible to antibiotics as a lower concentration of ABs needed harder for AB to enter into middle of biofilm to target the bacteria eg metal hip replacement: biofilm forms around the metal hip causing infection, no blood flow around the metal hip to take anti-microbial therefore need to repeat the surgery

Question 43

what is the impact of biofilms on the oil industry?

Answer 43

microbes attach to the steel and form biofilms biofilms corrode the pipes pipes then need to be replaced - expensive

Question 44

why would a microbe not have the same impact when grown in the presence of another microbe vs being grown individually?

Answer 44

more profound when together

Question 45

why would you need to find out what microbe it is that is causing infection when in the presence of other microbes?

Answer 45

need to find out what microbe it is causing the infection in order to treat it different microbes require different treatment plans

Question 46

how would you find out what microbe is causing the infection when in the presence of another microbe?

Answer 46

look at its virulence factors

Question 47

what is cell-cell signalling?

Answer 47

different ways cells communicate using different chemicals they produce

Question 48

where does the name quorum sensing come from?

Answer 48

need a certain number of organisms to be present before chemicals are produced

Question 49

what is quorum sensing?

Answer 49

a type of cell-cell communication chemicals thrown into environment (signal) microbes sense the signal and move towards it (food sources, upregulate virulence factors)

Question 50

what is quorum sensing an example of?

Answer 50

cooperation

Question 51

what is the principle behind social organisation of bacteria?

Answer 51

some bacteria produce products needed by all bacteria other bacteria dont produce these essential produce but use what the other bacteria have produced (cheaters, sense of hierarchy) happens especially in biofilms

Question 52

what is the evidence for electrical signalling between bacteria?

Answer 52

some form networks and can move electricity from one place to another could we harvest this electricity? is it an example of neural activity?

Question 53

what is meant by the term epidemiology?

Answer 53

the effects of pathogens on populations | a measure of when and where they occur

Question 54

define the term incidence

Answer 54

the number of new cases of a disease in a given area/population

Question 55

define the term prevelance

Answer 55

the total number of new and existing cases

Question 56

how are incidence and prevelance expressed

Answer 56

as a ratio | I:P