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Flashcards in Transmission of Infection Deck (41)
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1

what are the basic principles of the chain of infection?

- Infectious agent
- Reservoirs
- Portal of exit
- Means of transmission
- Portal of entry
- Susceptible host

2

what does virulence mean?

ability of the microbe to cause disease

3

what does dose mean?

number of microbes entering the body

4

what factors are included with regards to virulence?

• Exotoxins
○ P.gingivalis (protease)
○ S.aureus (endotoxin & leukocidin)

• Endotoxins
○ Lipopolysaccharide
(P.gingivalis & E.coli)

5

dont know how to question this / how to understand it but here we are to learn x

infectious dose:
Usually expressed as infectious dose 50 (ID50)
• TB = 1 bacillus
• Syphilis = 57 bacteria (ID50)
• E.coli 0157 = <10 cfu
•Influenza virus = <10 (tissue culture ID50)

6

name reservoirs where microbes can live

- humans
- animals
- fomites
- environmental

7

where does most pathogenic microbes that infect humans come from?

other humans

8

give an example of a human pathogen that comes from animals

anthrax

9

give an example of a human pathogen that originates in the environment

clostridium tetani spores in soil

10

what are fomites

Contaminated objects or surfaces
Usually act as a bridge between health care workers and patients
Eg phone, keyboard, medical equipment surfaces, house keeping surfaces

11

what are the different sources of infection?

> patients in the acute phase of an infection = easily recognised eg influenza, common cold

> patients in the podromal phase of an infection = not easily recognised eg measles, mumps, chickenpox

> healthy carriers of pathogenic organisms = not easily recognised includes convalescent carriers and asymptomatic carriers eg HIV, Hep B and C, herpes viruses

12

what is the incubation period

the time between contamination and the development of symptoms
varies widely for different infections

13

what is the problem with longer incubation periods

longer time periods when the infecting microbe may be spread to others
means a greater spread of the disease because of more human contact

14

define asymptomatic carrier

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

15

why are carriers dangerous in the spread of diseases

they are usually unaware of their infectious state

16

define colonisation

is the presence of bacteria on a body surface (like on the skin, mouth, intestines etc) with growth and multiplication without causing disease (clinical expression of the infection) in the person

17

define infection

the invasion of a host organism's bodily tissues by disease causing organisms

18

define exogenous

growing or originating outside an organism
caused by microbes from external soruces eg influenza

19

define endogenous

growing or originating within an organism
caused by members of the normal flora if
- flora becomes ecologically harmful due to population / gene expression shifts eg periodontal disease, dental caries
- they become displaced to another body site or are allowed to invade deeper tissues eg post surgical infections

20

explain portal of exit

microbes must escape from the source to colonise a new host

21

what are the different modes of escape (portal of exit)

natural
- coughing
- sneezing
- tears
- urine

artificial
- blood donation
- dental handpiece aerosols

22

classify pathogens in the 4 hazard groups

- ability to cause infection
- severity of the disease that may result
- risk of population spread
- vaccine and treatment availability
(venn diagram - where these 4 things over lap = extremes = ebola outbreak)

23

what is R0

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

24

explain R0 < 1

infection will die out in the long run

25

explain R0 > 1

infection will be able to spread in a population
higher R0 number = bigger the risk there is of an infection

26

what factors affect R0

- duration of infectivity
- infectiousness
- number of susceptible people

27

what is influenza

infectious agent
RNA virus with segmented genome
3 types = A, B, C
types A and B cause major outbreaks
> X2 surface glycoproteins
- hemaglutinin H1-15
- neuraminidase N1-9

28

what is pathophysiology

the disordered physiological processes associated with disease or injury

29

what is the pathophysiology of the influenza virus

infection of upper and lower respirator tract
release of cytokines (IF and TNF) = fever, headache, fatigue

30

explain the infection of influenza

uncomplicated
- fever
- cough
- headaches
- fatigue

complicated
- bacterial pneumonia
- ear and sinus infections
- worsening of chronic medical conditions like asthma and heart disease