10. Micro-organisms in Disease Flashcards Preview

EMS - Mechanisms of Disease > 10. Micro-organisms in Disease > Flashcards

Flashcards in 10. Micro-organisms in Disease Deck (28):
1

what is pathogenicity?

the capacity of a micro-organism to cause an infection

2

what are the characteristics of a pathogenic organism?

transmissibility
establishment in or on a host
harmful effects
persistence

3

what is virulence?

the degree to which a micro-organism is able to cause disease. allows a relative description of pathogenic potential

4

what is LD50?

dose of an organism that all cause death in 50% of the animals exposed to it

5

what is ID50?

dose of an organism that will cause infection in 50% of the animals exposed to it

6

what is infectivity?

the ability of a micro-organism to become established on or in a host. either accomplished with the help of a microbial ligand or a host cell surface receptor

7

what are virulence factors?

components of micro-organisms that result in harmful effects

8

what are virulence mechanisms of micro-organisms?

facilitation of adhesion (adhesins)
toxic effects (toxins)
tissue damage (aggressins)
interference with host defence mechanisms (interferins)
facilitation of invasion
modulation of the host cytokine responses (modulins)

9

when are endotoxins released?

damaged to dead bacterial cells

10

what is the active component of an endotoxin?

lipopolysaccharide (LPS)

11

how does LPS harm the body?

binds to a number of host cell receptors and induces a range of uncontrolled host responses

12

where are endotoxins found?

bacterial cell wall

13

what is the effect of exotoxins?

systemic inflammatory response syndrome, involving
1. uncontrolled t lymphocyte response
2. uncontrolled activation of the clotting cascade
3. uncontrolled activation of the complement

14

what are the effects of an uncontrolled t lymphocyte response?

cytokine release
fever, riggers, hypotension, tachicardia, collapse
cardiac and/or renal failure

15

what are the effects of uncontrolled activation of the clotting cascade

disseminated intravascular coagulation (DIC)
depletion of clotting factors
bleeding tendency

16

where are exotoxins food and how can they be tackled?

produced by living bacteria
patients can be treated by actually killing the bacteria

17

which organism causes botulism?

clostridium botulinum

18

how does c. botulinum spread?

ingestion of pre-formed toxin
infection of dirty wounds
GI colonisation in infants

19

what are the effects of botulism?

causes flaccid paralysis because it blocks muscle contraction

20

what is the clinical presentation of botulism?

diplopia
dysphagia
dysarthria
dry mouth
death due to respiratory failure

21

what organism causes tetanus?

clostridium tetani

22

what toxin is produced in tetanus?

tetanospasmin

23

what are the effects of tetanospasmin?

binds to nerve synapse, inhibits release of inhibitory neurotransmitters in the CNS
eventually leads to death due to respiratory paralysis

24

what are the effects of strep. progenies virulence factors?

promote connective tissue breakdown and aids invasion

25

what are the syndromes caused by strep. pyogenes?

streptococcal sore throat
erysipelas
necrotising fasciitis
scarlet fever

26

how does s. pyogenes evade the immune system?

m protein binds to fibrinogen and masks the bacterial surface, blocking complement binding and opsonisation

27

how does s. pneumoniae evade the immune system?

its polysaccharide capsule inhibits opsonisation and therefore phagocytosis

28

which pathogens are intracellular?

mycobacterium tuberculosis
salmonella typhi
listeria monocytogenes