MOD 11 & 12 - Micro-organism in Disease Flashcards Preview

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Flashcards in MOD 11 & 12 - Micro-organism in Disease Deck (20):
1

definition of pathogenicity

capacity of a micro-organism to cause an infection

2

what are the 4 main criteria which makes up the pathogenicity

Transmissibility
Establishment in or on a host
Harmful effect(s)
Persistence

3

definition of virulence

the degree to which a micro-organism is able to cause disease

4

definition of infectivity

the ability of a micro-organism to become established on/in a host

5

how can micro-organism become established in a host

through ligand-receptor binding eg E.coli fimbriae - glycolipids on human uroepithelial cells

6

what are virulence factors?

components of micro-organisms which result in harmful effects

7

what are some of the examples of virulence mechanisms

1 - facilitation of adhesion 2 - toxic effect
3 - interference with hot defence mechanisms
4 - tissue damage
5 - facilitation of invasion
6 - modulation of the host cytokine responses `

8

what are the 2 virulence factors for bacteria?

Endotoxin, Extotoxin

9

what is endotoxin

component of gram -ve bacteria cell wall eg E.coli & neisseria meningitis

10

how can endotoxin cause damage

released from damaged/dead cells & have lipopolysaccharide - binds to a number of host cell receptors & induce a range of uncontrolled host response

11

what are the responses of the host

Systemic inflammatory response syndrome (SIRS)

- Uncontrolled T-lymphocyte response (fever, hypotension, tachycardia, cardiac failure)

- Uncontrolled activation of the clotting cascade - bleeding tendency & depletion of clotting factors

- Uncontrolled activation of complement

12

what are exotoxins

proteins produced by living bacteria

13

what is an example of a bacteria for exotoxin production

botulism - clostridium botulinum - contaminated food, infection of dirty wounds, GI colonisation

14

how can botulism cause damage to the body

by releasing exotoxin - which inhibit the release of ACH in neuromuscular junction - ie no muscle contraction

15

what are the clinical presentation of botulism

diplopia, dysphagia, dysarthria, dry mouth, death (respiratory failure)

16

what is Tetanus an example of endotoxin or exotoxin

exotoxin

17

what causes tetanus

clostridium tetani - infection of dirty wounds

18

how can tetanus cause damage to the body

tetanospasmin (toxin) - binds to erve synapses - inhibits release of inhibitory neurotransmitters in CNS (can cause death by respiratory paralysis)

19

what special virulence factor does streptococcus pyogenes have?

VF prmotes connective tissue breakdown and invasion

20

what can streptococcus pygenes cause

strep. pyogenes syndromes - streptococcal sore throat, erysipelas (large raised red patches on the skin), necrotising fasciitis, scarlet fever