Transmissions of Infections

Question 1

what are the steps of the chain of infection?

Answer 1

• infectious agent
• reservoirs
• portal of exit
• means of transmission
• portal of entry
• susceptible host

Question 2

what is meant by virulence?

Answer 2

the ability of the microbe to cause disease

Question 3

what is meant by dose?

Answer 3

• the number of microbes entering the body

Question 4

what is dose normally expressed as?

Answer 4

infectious dose 50 (ID50)

Question 5

how do you know if a microbe is MORE infectious?

Answer 5

a LOW ID50

Question 6

what are exotoxins?

Answer 6

a toxin released by bacteria into the external environment

Question 7

what is an endotoxin?

Answer 7

a toxin that is released from GRAM NEGATIVE bacterial cell walls

Question 8

what is an example of a periodontal pathogen?

Answer 8

P. gingivalis

Question 9

what is a leukocidin?

Answer 9

a white cell toxin

Question 10

what is an enterotoxin?

Answer 10

a toxin produced in/affecting the intestines

Question 11

give examples of reservoirs:

Answer 11

• humans
• animals
• environment
• contaminated surfaces

Question 12

give an example of an environmental pathogen?

Answer 12

CLOSTRIDIUM TETANI spores in soil

Question 13

what are the different phases of an infection?

Answer 13

• patients in acute phase
• patients in the prodromal phase
• healthy carriers

Question 14

what is meant by the incubation period of a pathogen?

Answer 14

the time between contamination and the development of symptoms

Question 15

what do long incubation periods permit?

Answer 15

• longer time periods when the infecting microbe may be spread to others
• greater spread of the disease due to more human contact

Question 16

what is an infected person that shows no clinical evidence the disease called?

Answer 16

asymptomatic carrier

Question 17

what is meant by colonisation?

Answer 17

the presence of the microorganism in/on a host with growth and multiplication but without overt clinical expression (infection)

Question 18

when is meant by an endogenous infection?

Answer 18

infection caused by members of the normal flora

Question 19

give an example of an endogenous infection:

Answer 19

periodontal disease

Question 20

what is meant by an exogenous infection?

Answer 20

infection caused by microbes from external sources

Question 21

give an example of an exogenous disease:

Answer 21

influenza virus

Question 22

modes of escape from the source can be?

Answer 22

• natural

* artificial

Question 23

example of a natural mode of exit?

Answer 23

• coughing/sneezing

Question 24

example of an artificial mode of exit?

Answer 24

blood donation/dental hand piece aerosols

Question 25

what are the 4 hazard groups that human pathogens are classified into?

Answer 25

* ability to cause infection * severity of the disease that may result * vaccine & treatment availability * risk of population spread

Question 26

what is meant by the “R” number?

Answer 26

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

Question 27

what factors affect the “R” number?

Answer 27

* duration of infectivity * infectiousness * number of susceptible people

Question 28

why are aerosols problematic in reverence to infection?

Answer 28

aerosols can aid in transmission

Question 29

how can aerosols in dentistry be mitigated in an attempt to slow down/prevent transmission?

Answer 29

* use of rubber dams * high/low volume aspiration * surgery ventilation

Question 30

how long does Influenza A&B survive on steel and plastic?

Answer 30

24-48 hours

Question 31

how long does Influenza A&B survive on cloth, paper & tissues?

Answer 31

8-12 hours

Question 32

what are the 5 moments for hand hygiene within the practise?

Answer 32

1. before touching a patient 2. before clean/aseptic procedure 3. after body fluid exposure 4. after touching patient 5. after touching patient surroundings

Question 33

give examples of human portals of entry:

Answer 33

* respiratory tract * gastro-intestinal tract * open/surgical wounds * medical devices/sharps injuries * sexual contact

Question 34

why are susceptible hosts more at risk of infection?

Answer 34

* underdeveloped immune system * declining immune system (elderly) * breaks in the skin * medical devices