transmission of infection

Question 1

what is the definition of virulence?

Answer 1

the ability of the microbe to cause disease

Question 2

what is the definition of dose?

Answer 2

the number of microbes entering the body

Question 3

how is dose usually expressed?

Answer 3

infectious dose 50 (ID50)

-international standard

Question 4

what are the virulence factors?

Answer 4

exotoxins and endotoxins

Question 5

give 2 examples of exotoxins

Answer 5

P. gingivalis
-protease
-periodontal pathogen
S. aureus
-enterotixin & leukocidin
-white cell toxin

Question 6

what is an endotoxin?

Answer 6

produced by bacteria
secreted into external environment
located in gram - cell walls and released

Question 7

give two examples of endotoxins

Answer 7

lipopolysaccharide

• P. gingivalis
• E. coli

Question 8

where do most pathogenic microbes that infect humans come from?

Answer 8

other humans

Question 9

where else can human pathogens come from? give examples

Answer 9

animals
eg anthrax
environmental
eg clostridium tetani spores in soil
fomites
contaminated objects or surfaces

Question 10

what is an incubation period?

Answer 10

the time between contamination and the development of symptoms
-varies widely

Question 11

what phase of infection is the source easily recognised?

Answer 11

acute

Question 12

what 2 phases are the sources not easily recognised

Answer 12

podromal- asymptomatic

healthy carriers

Question 13

what do long incubation periods permit?

Answer 13

longer time periods when infecting microbe can spread

greater spread of disease because of more human contact

Question 14

what is an asymptomatic carrier?

Answer 14

an infected person with no clinical evidence of disease, though signs and symptoms of the disease may have been evident

Question 15

what is a carrier?

Answer 15

usually not aware of infectious state

Question 16

what is colonisation?

Answer 16

the presence of micro-organisms in or on a host with growth and multiplication, but without any overt clinical expression

Question 17

how does colonisation become infection?

Answer 17

no treatment

Question 18

how can disease be caused by members of the normal flora?

Answer 18

they become displaced to another body site or are allowed to invade deeper tissues
or
flora becomes harmful due to population/gene shifts

Question 19

what is the portal of exit?

Answer 19

microbes must escape from source to colonise new host

mechanisms vary

Question 20

what are the 2 modes of escape?

Answer 20

natural
-eg cough, sneeze
artificial
-eg blood donation, dental aerosols

Question 21

how does the COSHH classify human pathogens into 4 hazard groups?

Answer 21

ability to cause infection
severity of resulting disease
vaccine & tx availability
risk of population spread

Question 22

what is the R number?

Answer 22

the number of cases one case generates on average over the course of its infectious period

Question 23

what happens when Ro<1?

Answer 23

infection will die out in long run

Question 24

what happens when Ro>1?

Answer 24

infection will be able to spread in a population

Question 25

what factors affect Ro?

Answer 25

duration of infectivity infectiousness number of susceptible people

Question 26

how do large particles spread? (>10microm)

Answer 26

droplet and splatter

Question 27

how do small particles spread?

Answer 27

aerosol

Question 28

how can dentistry generated aerosols be mitigated?

Answer 28

rubber dam high/low aspiration surgery ventilation

Question 29

what are the 5 moments of hand hygiene?

Answer 29

``` before touching px before clean/aseptic procedure after body fluid exposure after touching px after touching px surroundings ```

Question 30

what are the portals of entry? give examples

Answer 30

``` respiratory tract -flu GIT -salmonella/norovirus open wounds -staph aureus medical devices/sharps injury -hep. B sexual contact -HIV ```

Question 31

what are the routes of entry for influenza?

Answer 31

respiratory inhalation direct contact in-direct contact

Question 32

what is a susceptible host?

Answer 32

a person who is at risk of infection as they are unable to fight the infection

Question 33

give examples why a host cant fight an infection?

Answer 33

underdeveloped/declining immune system disease/drugs that impair host defences breaks in the skin medical devices

Question 34

what are the risk groups for complicated infections?

Answer 34

elderly, young children, pregnancy, chronic medical conditions